I'm happy with the 24 hour limit too. When it was first introduced (after having unlimited edit time) I didn't think it would give enough time, as I'd sometimes returned to previous threads to discover spelling mistakes that I could not live with.
However I am used to the 24 hour limit and find it works well.
I know some people do alter their posts but I have not noticed the substantial content changes others have mentioned.
I often fiddle with my posts after posting, but generally to make slight changes or to add something (and I try to include the word 'added'). It has even happened that I have posted something which, upon reflection, I think may not be appropriate, or may be open to misinterpretation, so I choose to delete or substantially change it. I must add that this has never messed up the flow of a thread but I like to have some flexibility to make changes if I wish.
15 minutes to change a post would not be enough for me. On some fast moving threads even 15 minutes can see numerous other posts made. People can always chip in and say that a particular post has been highly edited hence replies may not make sense ....
I thought that an edited post showed the time it was last edited?
I do quite a lot of rootschatting on my ipad with a small text window and sometimes have to rush a reply and return later to find lots of typos. How embarrassing.
I think that removing or reducing the ability to edit your own post may lead to "bitty" posts where you will have to say "I forgot to add such and such to my previous post", even if there have been no other replies, or any replies given do not relate to what you have posted. As it is now, you could return to your post and add whatever you wanted to add. It will also give the moderators more work to do with people requesting them to make changes to their posts.
Sorry this is a bit long winded.