lots including Kubota B's, L's, cat, etc.. over many years
some bleed down / drift is somewhat normal and can be expected.
caused by small internal leaks in seals of cyl or valvles, etc... Generally increases with age, use and/or abuse. I had a guy who seemed to keep pressure on too long when working after max. stroke had been reached and IMO his use would accelerate bleed down of my equipment.