I field strip each time I clean my pistol. It is easy to do and takes under a minute to accomplish. I also like to visually inspect the parts for signs of unusual wear. I always clean the barrel from the chamber end (don't want to take any chances on damaging the barrel crown). Every second time I disassemble, I remove the firing pin and extractor and detail clean them as well (the extractor can get pretty gunked up by that point). This may border on overkill, but I prefer a clean firearm on my side.
I always field strip mine, if for no other reason than to clean out the residue that collects in the mag well, slide, and frame rails. If I don't clean it off, the residue will turn into a gummy mess in the slide channel over time and interaction with the moisture in the air, and cause function failures.
It happens quicker in cold climates. It can be so bad that the slide won't even extract the empty.
The same thing can happen with the firing pin channel, so that the FP gets gummed up, causing intermittent firing failures due to light primer strikes.