Such guns should not need to be 'cleaned.' As noted, they need to be lubed in many cases and for blued guns, wiped down again. Redneck2 described it well. For dead stored, every six months may be fine. For home defense guns, it is good to check them much more often, and then because you do, wipe them down.
I have opted to use lithium grease instead of oil and I find that for those that can be greased that they don't need to be lubed if they aren't used, but blued guns still need to be wiped down for corrosion, fingerprints, etc.