Well, it depends on what that constant rate is, and what the "high" temp is. If it's the max fan speed, then it's only a problem if the GPU temps are dangerously high like 90+C. You actually won't risk doing damage until you're up over 100C with most chips.
If you've got it at max fan speed and you're still cooking the GPU, you either have a poorly mounted GPU cooler, poor air flow in your case, or some sort of malfunction. The GTX 960 is not exactly a high wattage part, so cooling it shouldn't really be a challenge for the massive cooler that's on there, which is probably why you don't see the fans spinning up to jet engine speeds.