If you read through the thread you will see where two separate mods gave two separate explanations for why there is a limit.
Yes, I saw the reasons, however, (if my memory serves me right) there is a facility to compare the different versions of the post that have taken place at each edit, so that really covers the ability for all to see what has been written in it...
So, I fail to see the necessity for a time limit on the edit facility...