In considering the future care of a P227, do some parts also share with the P229?

Different - barrel, recoil spring? extractor? Magazine

Same - all the little springs? Hammer? Sear?

How hard is it to maintain a P227 in the future? Especially small parts???

The only thing unique to the P227 is the grips and the mag. And, of course, the frame. Everything else is shared with either the P220 (upper and locking insert) or P226/229 (lower small parts).