I have been mining Siacoin with my GTX1070 for a couple days with very few breaks. Is it bad to run my GPU 24/7?
Stays cool around 47C but i occasionally get up to 52C, i give it a break for a couple hours per day.
Newer parts, anything from the last twenty years is best just left running. It is like a car in a way. You would be better just driving down the road than hitting the gas to full, backing off and shutting the car off, then repeating the process.
Find and set up the best environment and then let it be. Letting the monitors or monitors go to standby and hibernate, without any hibernation in the machine itself may give you a few extra hours of life in the end, but not that much. Just get things perfect and let them be.