If any poster needs to have a post edited for errors and the time has elapsed all you need do is say so and any one of the excellent mods around here can help you out. Might even be willing to.
Tiny has done so with errors in his TV Times and Strids has a couple of typos fixed for him as well.
If you wish to edit for content, you really should just make another post in the thread. We all write things that don't come out quite the way we meant and I don't think that restating your postion should be of any consequence not an admission of being wrong.
Far as I can tell there are only about two people around here who have ever been wrong, and I can't remember who they were!
if you make a few typo's and its still readable then just leave it! Thats what i do most of the time, sometimes i still go in and fix it.
Hint my AKA name Mr. Typo