My experience ~
I had my bow set for 62 lbs. and it shot 231 fps.
I decided to crank it up to a magical "69"lbs and it shot 238 fps.

After sitting in 23 degree temps for 5 hours and trying to pull the 69 lbs back, I realized I couldn't, so I had to get down out of my stand 20 minutes early.

Moral of my story... I went back to an easy 62 lbs, which I could pull back in cold temps, especially seeing I didn't notice much of a difference in drop out to 30 yards...