My exercises are lined up by priority and I am out of the gym in an hour or less. So if I don't finish my routine and I'm dragging ass that day, I lose the lowest priority exercises and still got in the most beneficial. as far as 5 5x5's, if you do the math that's 25 sets, which means you have 144 seconds (just over 2 minutes) to devote to each set. I happen to think this kind of mechanical method of organizing your time is silly though. Some exercises take longer to recover from (squats and deads for example) and others simply do not (isolation exercises usually).