You're absolutely fine. Mid 80s is where you might be getting nervous with current nvidia cards. mid 60s is excellent.
You asked for examples, my 670 gets high 60s low 70s when operating alone (its overclocked pretty hard) under heavy load and high 70s/low 80s when I turn on SLI. I don't love the fact that my hot card consistently runs low 80s and peaks at 86 under heavy load, but I'm not really concerned with it burning out the card.
Enjoy your PC man!!