60 minutes. It is another one of the changes I made to discourage spammers. Turns out that one of their tactics is to make a post, wait a while for it to drop off the new posts radar, then go back and edit the post to add their spam.
Ahhh okay, makes sense. Course now everyone will know what a terrible typist I am...

I actually bumped this up to a week after spending some hours looking through a manual SQL query I made to identify possible spam edits. It might get removed again, though I will be sentencing myself to manually checking every post modified through each month to spot spam edits - the sunny side of doing that is that I can craft the query to ignore people we trust who do a lot of edits (Ash *cough* *cough*).