I clean mine based on what it looks like. Might be once a week, might be today and then again tomorrow, based on what it looks like when I pull it out of the holster. My pistols never stay in a holster over night. I look at them every evening when I pull it out of the holster and lay it up for the night. If it looks like it needs cleaning I field strip it and wipe/brush it off and re-lube, wipe the outside surfaces off with an oily cloth. The other day I was up under the house with the XD. When I took it out of the holster I could hear the dirt "crunching" as I pushed the grip safety in - time to clean it. The last couple weeks, when I get a chance, I've been working on an under the mud room storage system for the deck furniture, junk, etc. my wife decorates the deck with all summer. A couple days the XD was pretty well coated (back end of it) with sawdust. Came in, cleaned/lubed and put it up for the night.
I used to carry a spare CZ magazine (EDC) in my pants pocket. Decided to unload it one day (don't remember why) and the first few rounds came out and then the rest hung up down in the magazine. Yup, pocket crud. Got the rounds out by smacking it on the table (plastic base, oak table) to jar them loose. Then took the magazine apart and was amazed all the pocket lint/crud on the follower, inside walls, etc. Ordered two kydex magazine pouches that day. One for EDC (.40 S&W P07) and one for open carry around my house/property (9MM P01). No more pocket back up mag. carry for me.
I sweat so bad in the summer that I sometimes have to field strip/wipe down my P07 after just a few hours in the holster (IWB) under my shirt.
Oil stains are preferable to a malfunctioning pistol.