That's how I do it, 4Gains. I don't know if there's a special benefit of doing it all in one session, but splitting it up saves me time. Nice thing about stretching is that you don't need any lube.
Plus, I like to multitask my warm-ups so that my AM hot shower starts getting me warm. Then I go for the hot towel (on groin, but avoiding the scrotum) while shaving. This way, the warm-up hardly takes any extra time.