Here's what I do... its sort of a slight workaround....
If the 5 minutes expires and you see something u want to change, you still have like 1 minute to delete, so copy all your text, delete the post.... and then paste your text into a new reply box and make your changes and repost. It gives you an extra minute or so.... and you can repeat that trick over and over as long as you still have time to delete. The delete option expires in about a minute I think.