re: Grandpas rocking chair. What would you do?

If you don't want it to lose its "patina", simply clean it off as best you can and let it go at that.

If you want to be a bit ambitious, just rub on some oil finish, let it soak into the bare spots and wipe off any excess.

Sounds like you don't want to do a full blown recondition, but just a clean up.

ETA: I've done this in the past with a cloth and slightly damp with mineral spirits. That will remove any oils from the hands, body, etc. and not take off any finish already there. Just damp mind you, not wet.