If I'm storing mine for an extended time (until next season basically) I'll clean down to bare metal & oil the bore. When it's time to shoot them I'll run an oiled patch through them followed by a couple of dry patches so I'm shooting with a very, very light coat of oil in the bore. After that I don't clean the bore again until I put them up for next year, or after about 50 rounds if it's one I shoot a lot.
I live in the most humid place on earth and haven't had any trouble with fouled bores rusting. Smokeless powder residue doesn't absorb water like black powder residue. It seems to have protective qualities by itself. I'll caveat that with most of my barrels are stainless.
