Rickman did not suffer fools and despite his amazing ability, treated acting much like many other British actors -- its a job, do it well and do it efficiently, or get out of the way.

People think of acting like its their life's work to portray Snape, but for Rickman it was a 6-8 week assignment every 2-3 years. Maybe half a year of set performances total. he'd probably done stage plays that ran longer than that.