I don't do it often or anything but maybe once a year, I'll throw a little wire hook in the drill, spray a bit of WD40 in the bottom of a yogurt container or something, and soak all the swivels overnight, and then put the hook through the swivels one at a time and spin them for a bit.
It's probably pointless but I just figure it'll burnish any little bits of corrosion off the surfaces, and keep the action smooth.
Anyway, maybe once a year I'll dunk them.