Most reputable websites that I'm familiar with all have a limited editing period. Some have one as short as 3 minutes, while others have a period as long as 15. We're currently set at 10 minutes, and I don't see that changing any time soon.
That said, I do believe that a user should be able to edit their post title as well when editing a post, so we will look into making that possible.
Otherwise, I always tell people to review what you wrote (we do have a preview option when creating a post) to be sure that you are happy with it before posting it, because once you do, that's it . . . it is out there for the world to see.
Ten minutes is plenty of time to look over something you wrote for a fix.
What they teach in school is, "if you don't want anyone to read it, then don't post it online; always make sure you read and re-read what you write before pushing the submit button"
Josh