No, he says he wanted Eternal Life as a response to 18–As in, the reason why he’s a robot is because, according to him, it’ll make him live forever.
Yes, however we see pretty clearly in Future Trunks’ timeline that they don’t age whatsoever. They killed everyone when Gohan was just a kid, and they lived up until Trunks was nearly a grown man, age wise. They are quite effectively, although not literally, ageless. Thus, him saying he can get Eternal Life from his procedure (which makes him more machine than them), is well founded. Especially since he can just…keep creating bodies.