I don't know if putting resistors in series would help you. It's not so much a question of power savings. It's just that you are running the 555 at it's absolute maximum voltage rating and generally, that's something I try to aviod. Maybe I'm being too conservative and someone else can chime in and tell you it's fine. Personally, I would decrease the supply volatge of the 555 and up the gain on the op amp to achieve your desired output. But if you have tested the circuit and everything works well without getting hot, it's probably OK.