Safe temperature limit for GPU

[Tombstone_actual]

Hi, I use a Zotac gtx 960 amp 4gb edition gpu and it hits 80°C in most cases if the fans are kept at auto during summer. I use msi afterburner to manually tweak the fan settings at 1:1 and it hovers around 70-75°C mostly. So there's a slider named 'Temperature limit' and I had kept it at 65°C and automatically the 'power limit' slider came down to 46%. If I keep the temperature target at 70 the power remains at 64%. While it does a great job keeping the temperature at bay but I'm worried if under-powering the card would affect its longevity or performance in any way(so far I haven't noticed any change in performance). Is it okay to use the temperature targets like this? Or is it okay to keep the card at manual? Links to the pics of my case:

and

Thanks in advance.
My full pc spec:
Cpu: Intel Core i7 6700
Gpu: Zotac gtx 960 amp 4gb
Ram: Kingston Hyperx fury 8gb 2133 x2
Mobo: Gigabyte B150M-D3H
Psu: Xfx pro 650w gaming edition bronze 80
Hdd: Wd 1tb blue
Case: Cooler master N300
Cooling: 3x 120mm cooler master sickle flow for exhaust and hyper 103 for cpu. (the case is well ventilated and cables are well managed to keep a negative air pressure inside)

 

[Luck1112]

It is very strange that a card such low power and with a custom design double fan heats so much. Try to remove the dust and improve air circulation with more intake fans. DO NOT make any power limit: it will sensitively reduce the performance of the card, so don't change the temperature max either. Play with fan spees settings. Up to 75c is ok, 80c should be the temp reached only for seconds