In the spring I bought a Sig P239, and started attending some local steel plate matches. Each match had me go through 150-200 rounds or so, and I went almost every week. I decided that I was going to wait for the gun to fail before I cleaned it. It got really really dirty. I shot nothing but WWB, the mags were dropped into the sand each time, and I'd just wipe the side on my pants, reload, reinsert, sand got everywhere in the thing, and I'd just keep it loose in my range bag when I brought it home.
It never did misfire or otherwise fail to work. Eventually, in late august, I decided to carry it one weekend, so I gave it a good thorough cleaning beforehand.