I don’t believe it’s constrained by those time limits, so anyone in a group with that ability can edit all posts no matter what age.
Though I always find the best way to be sure is to give it a whirl. 
That way you can be confident in any beefed up abilities you’re granting to your members. If you create a test user and add them to a test group with the ability and see if you can edit a post from a few months back (depending on your TL2 edit window) that should let you see what’s what. 