Richard, it used to be longer but now I believe there's a 2-hour time limit for owner editing of posts.
If you ever need something edited later on, you can stickymail the mod or an admin to edit it for you, and we can just put a notation "edited per member request." I've had to do that to take stickymail notification off for people a couple of times when threads ended up hitting over 100 posts.
We're always glad to help however we can, so don't hesitate to ask if there's ever anything.
The theory on editing, is to give members enough time to fix typos and spelling errors, but not enough to change the context of the post as followup messages may depend on the message for reference. Currently set at 3hours.