No, I would keep it at around 80% all the time unless you have free electricity. If that is the case, then yes get a room fan to blow over them to cool them off some.
If like most of us you do pay for electricity, then drop it to 80% and leave it there. While you do lose a bit of hash rate, your efficiency also will go up so you are getting a better Sol/Watt ratio.
With a bit of tweaking and at 80% I can maintain close to a 700 Sol/s hash rate on a 1080Ti while dropping the wattage, and thus heat, down quite a bit, saving some electricity in the meantime. Plus they are quite expensive cards to burn up right away, and even in the time it takes to RMA one you would probably lose more hash rate then just running them a bit lower.