It used to be that you couldn't edit your posts after 24 hours, but now you can edit any of your posts regardless of how old they are.
Another forum that I'm a member of allows you to edit your posts at any time, but if you do it more than 60 seconds after posting, then the post automatically shows that it has been edited regardless of whether you give a reason or not. This gives you a minute to fix up any typos. Here, it only displays the post as being edited if you type a reason for the edit in the optional box.
I don't use the box unless I'm altering the original text for clarification. If I'm fixing a typo, or spelling, then I don't show an edit, and if I'm adding more material, then I start with the word 'Edit;' at the bottom of my post.
I feel that this isn't 'cheating' in any way by altering what I've originally said.
Edit; Sometimes in my lengthier posts, when I'm helping someone out by explaining something, I might make quite a few additions after originally posting, since I often think of more tips that I can add.
Edit 2; I usually number my edits if there's more than one.
Edit 3; I've never 'pulled' a post, unless it was an accidental double post. Once you've said something, it can't be taken back, and if I've put my foot in my mouth, then I just have to apologize.
