I've finished all 18 and have stopped resetting. I get a 2% increase from a reset. Really not worth it now. You can stop at any point you have the patience for. You are right that they will likely increase the warp in the future, but that is probably when the next girl/girls come out. When they do that, they will also add levels for skills and possibly more expensive gifts. If I had unlimited resources, I would spend on Anya to make her my top girl and just leave the taco suit on her. That is so funny!