Sorry I didn't see this sooner. I carried SIG 226s and 220s for many years on the job and went thru their armorer school. Basic field stripping, cleaning, lubricating, etc., should be done after serious use, extended carry without firing, exposure to weather, etc.
As to detailed stripping and cleaning, we/I always did mine yearly.........usually this was after firing 500-1000 rounds minimum over the course of the year. 220s/226s need NEW roll pins NOT THE OLD ONES if you detail strip to the point of removing the breech block in the slide. Be sure to make sure the openings on the roll pins oppose each other (one at 9 o'clock, the other at 3 o'clock).
Every 5 years (please, without fail) replace the firing pin spring, trigger return spring and the firing pin block spring!!! Nearly all civilians don't know any of this. Most major police agencies who carry these guns exclusively mandate it---and SIG recommends it. I know one police officer who never knew this, nor performed the 5 year update, and shot it out with a bank robber armed with a Browning Hi-Power........fortunately our officer friend drilled the bad guy with the first shot (broke arm, ribs, and got the lung).....however, when the bad guy tried to switch hands and shoot, our friend kept pulling the trigger but nothing happened. Fortunately the bad guy fell over from blood loss. BROKEN TRIGGER RETURN SPRING.
Sorry for what sounds like a lecture in retrospect...didn't mean it to sound that way. I now carry a Glock only because I have to by policy; SIGs are great guns, but this is what is required and is no big deal once you learn how. I have a very soft spot for 220s.........
Take care
RR