That is just fine for that card. In fact, it's pretty low considering the max temp is rated at 97C. If you use afterburner or precision X you could set up a profile to keep the fan at a lower speed, while in turn decreasing the GPU fan noise and let the temp go up in the 60Cs or 70Cs and still be fine.
Seems odd that someone would tell you to let the temps go higher, but you have a lot of room to work with. The reduction in fan noise is always nice unless you always play with headphones on. Then there's no need.