How often do you need to grease the crank? Haven't done maintenance on my bike in years.  Recently cleaned it up and repaired some spokes.  Greased the front and rear wheel bearings and degreased the chain.  Looks good but only thing didn't do was grease the crank.
It is likely, unless your bicycle is quite old, that it has sealed bearings in the crankset, so there is no real need to grease them yourself. It is good practice to visually inspect and clean them regularly, but they do not need deep maintenance unless you encounter rough movement or an unusual sound coming from them.

Ciitation: Bicycle industry work experience.