Maybe we never said why the edit feature was limited to an hour.
There were some situations with some, let's say contentious posts, that got some conflicting replies. The OP's went back and edited posts making the following posters appear to be the troublemakers. As Mods, we ended up being referees all too often. It's no fun to be throwing flags, pulling red cards, pointing to the corner and showing some the door.
Because of this it was decided to limit the edit time to an hour for OP's to fix or add to posts. We originally started with a 5 minute limit and soon realized 5 minutes was simply too short a time, especially with wordy and illustrated posts. So 1 hour was the compromise result.
As far as how long the edit time is unlimited, we're playing it by ear right now. We want those that have the old pics and desire to fix the threads to have the time. If anything hits the fan as it did before, the limits will be reinstated.
Hope that explains our thinking.