Actually the edit feature remains for many hours although the post will be time-stamped if edits are made after the first 15 minutes. I try and make at least one edit after the time stamp on every post just for the fun of it. After some number of hours the edit feature also disappears, something like 24 hours, and then only a moderator or administrator can change or remove it. Of course of it was offensive we would have already deleted it well beforehand, but occasionally a user makes a boo-boo and wants their post deleted which we try and accommodate for a small fee.