I generally like to have the fans hit 100% at 80C. because as I said before, 80C is kind of the saftey limit for everyday use.
otherwise I would adjust it balancing temperature and noise you can withstand. if you're ok with 60% fan speed and that keeps your card at 65C when you game, great! if your card goes to 75C at 60% and you can't stand to hear the fans at 80%, then well, there's nothing wrong with 75C
so yeah, I generally keep it fairly flat and have it go up pretty quickly between 65-80C