Its mostly a bonus... you are getting experience with different ways of thinking which will aid you in all future jobs. Still I do think there is a sweet spot where you do learn by staying put. That will naturally happen for you. The bigger down side is you dont want to have too many short jumps on your resume as future employers will either see you as an immediate flight risk (and not hire), or see you as a problem child that cannot hold on to a position (no one really knows why you left each position, even if you explain it) so do be careful of looking too flighty