The slower the better ride. I thought the effect was the square of the speed change but was corrected in an earlier thread about this.
I see no reason not to slow down a bit if it gets bumpy. The TPS is for severe turbulence, not coffee-spilling. If you've got 60 knots on the bottom foot, slowing down will smooth out the ride, and if climbing, will reduce your time in the bumps. Win win.