I, speaking as a member here, not as staff, think that things as they are are fine : members have 24 hours to edit posts as it stands now so you can add attachments you might have forgotten previously.
I am also thinking in terms of people with suspect intents in a forum : I was a member in a forum where we could delete our posts. One member would post offending remarks then delete his posts, so when you complained to the forum staff, you had no proof. After a time, we knew he'd do stuff like that so we had to catch his posts before he deleted them and take screenshots : eventually, the member in question was banned for his behaviour.
In Mac-Forums, you can edit out offending posts, it's true, but at least after five minutes it shows below the post that the text in the reply box was edited or altered : it won't show what was changed but at least we can all see that the member changed his reply.
So for those reasons, I think settings should remain as they are now.