Time to reply to the request is immediately ASAP.

Time to show the property depends upon what the showing instructions say (appointment only, 24 hours ,etc.).

  HOWEVER, remember that Buyers want to see the property today now, not at your leisure or whenever the Seller feels like it.  

Depends on when it comes in.  A few days ago I had a voice message that was left at 10:45 pm.  I responded first thing in the morning when I received the message.  

I use Showingtime for all my listings, so like Right Said Fred Griffin Florida Real Estate said, immediately!
Technology makes having to contact the listing agent to show an archaic waste of time. But let's say there are special circumstances. I'll give you an hour to reply before I start blowing up your phone, text, email and broker.
I am admittedly and devilishly the worst to keep waiting for a response because I'm often booking multiple homes and you're holding that up if you're not set up to reply quickly. Don't take the listing if you can't properly serve the listing.

that depends.  when I get a showing request at 9 or 10 pm I'm not calling my sellers to set that up until in the morning.  Otherwise a couple of hours.  I may be busy when it comes in.

For vacant homes, we set it up as "vacant, go direct" in the MLS.  For occupied homes, I respond as quickly as possible to at least let them know I'm reaching out to the seller.

Our MLS uses Showingtime so most of the time it is immediate. If we need longer time it is usually for the removal of a dog. Most of our showings also say 4 hr notice as an example.

LOL - like Peter Mohylsky and Don Baker says "It depends".

Keep in mind that not only has the message need to get across to the LA or Showing Service. But also most likely needs to get Confirmed via the Sellers, which seems to be the hardest task of all...

ASAP.  So easy to do with showing time.  No excuse not to.

Wanda Kubat-Nerdin - Wanda Can!, it should be immediate(for the most part). Some take days, some may not even respond. 

OOPs! I misinterpreted the question yesterday thinking how much notice should OUR Buyers give us that they want to see a house.

I think it is all in the mind of the potential Buyer Wanda Kubat-Nerdin - Wanda Can! I had one, whom I had shown several homes, could not wait an hour as I was driving home on a stormy winter evening. I didn't kiss them goodbye... I kicked them in the ass goodby. 

It depends.  I have had email and text requests at all hours of the night.  But even if I'm with clients I generally can follow up on a text or call within the hour.  Occasionally I have a seller out of pocket for a little longer, but I try to follow up as quickly as possible. 

It all depends is the short answer.  I try to respond as quickly as possible but not all listing agents do the same.  

Depends.

We use Showing Time so getting a time for a showing should not be a problem.

If I am contacted directly, I would refer the caller to Showing Time. 

Fred Griffin Florida Real Estate summed it up well. 

     If the place is empty, should be only another showing at the same time delays the get right in. When tenants are renting and are not so hand stand happy about showings, that will create a delay.

     You can jump all over the listing agent but he or she has to work with what they have. That listing agent may be telling seller please talk to this renter who never finds it convenient to show. You want the owner or renter to know you are coming so the place can look it's best.

     I always strive for a day's warning for a place with a tenant and to only qualified buyers. And try to double up with back to back showings and then get out of their hair. Not too early, not too late and sensitive to someone lives here. Same with property owners, they have lives. Yes they want to sell but sometimes family emergencies take priority.

     This is another area where listing and selling agents can act professional and not malign the other agent or publicly and verbally let them have it with both barrels.

     Showing requests, you work with what you have and there is no set in stone law that 20 minutes, a day or whatever time frame is the gold standard.

It would depend on when I received the request. If it’s after 10 pm it will wait until morning. If it’s through the day I send it to my client via text or their preferred method of communication, then it would be as soon as my client responds back. If I haven’t heard back in a hour or so Icall my client. 

When someone hires me, then I am on duty to do whatever it takes & I charge for it. Apply the RRR or Richie reverse rule. If you don't, what good are you? How do you earn your fee and why manipulate your fiduciary?

Since we've used an automated system for appointments like Showing Time for more years than I can count now, I would say a response within an hour is acceptable. These days with so many sellers responding to a text request, I get responses in under 10 minutes. If it's not an automated system for appointments, it all depends on when that request came through. If someone calls me after a certain hour in the evening, they won't hear back until the next day, nor should they expect to.

As many have already said: "It depends".

In our region, we use ShowingTime, too.  So, often you can get an automated response very quickly.  Sometimes instantly, assuming the property is set up as a "go and show".  But if the sellers are 'notified', and need to respond, or the listing agent needs to accompany, it can often take longer... maybe an hour or two.

With a ShowingTime set up, (or something similar depending on your region), 2 days (as you mention in one of your responses) is ri-donk-u-lous!)

I can understand if the request came in late in the day, you might not hear back until early the next morning.  But otherwise, I'd be reaching out to the listing agent directly after a few hours, of radio silence.

Depends on how much the seller and their agent want to sell the property.  I try to get them approved as fast as my sellers will allow.

Same day, unless the call comes in late at night (post 8 PM)

It depends on if it is vacant or occupied.

Most of the time I hear back within 15 minutes unless it is late at night. There are some that go for hours and ShowingTime will escalate the request. Sometimes I have to track down the listing agent but that's rare. So, 15 minutes or you know you have a problem.

For me, i like to give the buyer agent/showing agent an immediate reply. Most of my showings are automated and instant. When i do have to call a seller, i let them know that so they are not wondering. Communication is everything and when there are more homes for sale then buyers soon, you will want those buyer agents calling you first

ASAP. I've had issues in the (recent) past with LA taking FOREVER to arrange a showing and then MAGICALLY an offer pops up. 

ASAP - and if you don't hear back within an hour, I would connect with someone else from the brokerage that has the listing to find out what's up.

ASAP; any delay might "smell" of unfair practices, especially in a very competitive market. 

ASAP right away up to 30 minutes.

While I typically try to respond within the hour (less than 5 minutes if/when possible), we get a lot of round the clock requests- being a global city and all. Streeteasy rolled out Showing Time earlier this year- and from my experience it's a total failure since we don't operate like the rest of the nation. Most showings require at least 24 hours notice with the seller's agent present as well as the (optional) buyers agent. Some buildings also have specific rules as to when buyers and brokers are permitted into the building.  It's also advisable for me to vet the buyer before submitting any buyers because there is so much applicable here that might not apply in most markets- i.e. are dogs allowed (if show breed and size are also qualifiers), or the apartment might seem to fit your budget- but the building requires 40% down or the monthlies might be 4x your mortgage payment and thus unaffordable..none of these might be obvious from the listing the buyer found online so I don't want to just set up the appt without chatting first. 

I answer in few hours and often minutes regardless it can be shown at a short notice or not, I believe that the acknowledgment and fast response is important and professional.  I noticed that the local busy agents with multiple listings usually answer promptly, some even instantly( of course, the most successful have assistants  for that:)  

Also, I would mention that most communication these days is happening via text. 

We use showing time in our area, but I try to always say at least 2 hours unless vacant.