Don't think that just because you have money you need to go back though. If your enemy in lane hasn't gone back yet, and he isn't giving you trouble, there is no reason to go back. If he leaves, and you have money/need health you should leave as well. If you leave before the enemy though, that just leads to them free farming. If you are lowish health and afraid of ganks though, go back after pushing a decent bit.
Also, as support, I would go back as soon as I have enough for a GP/10 item. Unless lane is going really well, then I will stay and harrass. But usually it is right when I have enough for my philo and a ward or 2.