programming drums -- full level

It really depends on the beat. The same like quantize, some tracks you use it and some you dont. Making beats is like painting, you dont always need the largest brush and all of your colors to get the painting right....

I have full level on all the time because my 1000 pads are dying. Sometimes use 16 levels for hats and also velocity setting on tracks. Most of the time I mix once recorded in DAW so don't spend too much time worrying about levels in the MPC.