Thank you, guys, for your feedback. I can't see any point to edit for 30 days other than people can delete sentences, so the entire thread don't make any sense.
You are welcome to PM me links or names to forums which allow unlimited editing time or 30 days editing time so I will have a deeper look into it.
For now, I have set the edit time for normal registered users to 15 minutes and 30 minutes for Business Angel users.