When you're done reading a particular thread, you can hit back (multiple times if necessary) to go back to the search results. They're not completely up-to-date, but it's usually close enough to last at least a few minutes.
Hitting back does NOT perform another search, so no, your post does NOT make any sense. I don't see anyone complaining about 270 second restrictions on hitting back button. The topic is timing between searches. Using the back button has absolutely nothing whatsoever to do with it. Read the OP.