I usually hit at about 60-70%. I get good topspin and I also get easy power with the knee bend and shoulder turning (which is less tiring than swinging as hard as you can in my opinion). That percentage usually keeps my opponents at bay, and I never get tired of running around because I'm only at 70%.
I save 100% for only one shot per match if I'm at least a break up. No need to waste energy.
I am an unpredictable player. Even I surprise myself with some of the shots I make.