Up to 75 C is an acceptable temperature to keep the cards at, but you are going to wear out the fans very quickly keeping them at 100%. Better to buy a $20 box fan and place it on top of the cards. It creates air flow around the cards and lowers the temp, so you don't need to run the card fans very high.
are you sure that setting the fans at 100% will wear out quickly? I have read that it should not affect to fans lifespan
I have to adequate my cooling, right now I have an open window and established a natural air flow between another open window. But I think I will try using a fan to push the air through the window
These cards finnally have double ball bearing fans. They should last a very long time, unlike previous Gigabyte cards.
I had several 970 and 1070 G1 Gaming cards and they all had crappy sleeve bearing fans that mostly died in about 6 months on the 1070s and about a year and a half on the 970s. Yeah, the 1070s had the worse fans.