What are we extending? A listing? I give them 2 weeks notice.
During a transaction? Financing delays? If you know a few weeks ahead that you'll need to extend . . . why wasn't a sufficient escrow period written into the contract? But I digress -- let them know as soon as possible that there is a delay.

Without having more specific information, my initial response is:  Not until you know you're going to need one.  My experience with extensions is that you shouldn't extend beyond the actual time needed because the lenders tend to consider it the new deadline... instead of closing as soon as possible beyond the original date.

I give the request as soon as I can, why wait?

It really depends upon what type of extension - is it for an appraisal? Inspection/repair response?

Listing or buyer broker agreement extension or an extension for the buyer or seller that can not close on time? Listing or buyer agreement, week of expiration if no offers are in sight (and you want to continue to work with them). On purchase and sale agreement as soon as an extension is found to be needed. -Kasey

Extension of what????????????????????????

It depends.

It depends on how quickly my seller is to respond.

Depends on what the extension applies to and who I am dealing with!

I ask before the notice to perform comes out, but often wait until past the deadline, except COE, that I ask for as soon as I'm notified officially of a delay.

Do it right first time so you do not have to ask for an extension. I have a listing the default duration was 90 days. The seller scratched it out for 30 days. After 32 days he accepted an offer and did not want to pay commission. In litigation right now.

Depends on circumstances.  Give us more details 

Usually the week of, provided the transaction has a history of all parties responding quickly

If it is a listing, one week, if it is a date on the contract, usually the day it expires.

If during an escrow, ASAP!  When buyers wait until the last minute on my listings, it pisses off my sellers and the buyer is more likely to get a per-diem if it's requested at the 11th hour.

As soon as it's known that an extension will be needed...

It's never too far out if you know it will be needed.

definitely be prepared at least couple of days prior to the deadline.

I usually start talking about it in the last couple of weeks.  I press for a decision the week of.

As soon as I know it is easy

At least two weeks notice and stay on top of it until you get the paperwork back. It it expires one or the other may be in default.

I typically ask as soon as it is known that one is needed. 

I have had people ask for them too far out and sent them back with instructions to speed it up and contact me later if they still need the extension.

A few weeks out is ridiculous. I would say a few days if it doesn't seem like it can get finished.

A good working realtionship is required at all times until COE. That's our job

5 to 7 days before it's needed, after you've been notified that it will be needed....

It is rarely the escrow closes exactly as planned when financing involved. If lender needs few more days or even few more weeks, this is what we ask for. 

It really depends on the situation. Typically we'd get it handled as soon as we are aware of an issue.

Depends.

As early as possible.

Don't wait til the last minute , some are slow to respond