Agree with ELE. Some posts may need discussion then we can edit previous post by adding the summary and conclusion of the discussion.
I used to write story in fan art section and need to edit some typos or little details sometimes. Five minutes after post will not be sufficient to find and rectify all. And like other writers, we need to edit link for new chapters uploaded in content list (usually our 1st post in the thread), that might be weeks or months before we upload the newest chapter.
I believe the same case for guide writers. They usually divide the guides into some smaller parts, need to make and edit their content list every now and then, also edit some of the guide after discussion.
I can't find the reason to limit editing time, it's frustrating 
