IIRC you can only edit your post for 5 days (can't find the setting in the current configuration...). You can't delete your posts after that time either. This is related to that part of our ToS:
Edit: found the setting: 1440 minutes (24hours)
Quote:You keep the copyright of everything you post on this forum (text in posts, and attachments such as images or code), but you give the forum owners the irrevocable rights to publish it here on this same forum. Admins and owners can reject requests to remove your contributions, and we can restore them if necessary.... which doesn't mean that we won't remove posts if requested, but this will be our decision
Edit: found the setting: 1440 minutes (24hours)