I've been using shimano spd's since 92 and wipe them with a rag and or a rag and a screw driver to wipe dirt out of crevices, usually when I clean and lube my drivetrain. I'll put a tiny drop of lube on the pivot points, just like I do with the pivot points of derailleurs, wiping off excess.
This and having the release tension at the lowest setting is all I do.

As invariably bring up, my 92 pedals are still in use.