As an experiment, I have tried both methods, cleaning after every smoke (to clarify, that means letting the pipe rest first, then taking it apart to clean--a day later, usually) and then kind of cleaning "as-needed," which turned out to be roughly once every two weeks.
I noticed not much a difference, but the problem lies in that last smoke that finally says, "Enough, I'm dirty, so you get moisture, garbage and filth rather than good smoke." I had no idea when that would be...after 10 smokes? 12? 20?
Playing Russian roulette wan't doing it for me any more. Though, rather than doing an alcohol swab, squeaky-clean after every session, much like one would care for a fine firearm, I resorted to somewhat lazier tactics, wherein after a pipe has rested, I take it apart, dry-swab the schmutz out of works quickly, and move on. This lasts me close to a month of decent smoking, provided adequate rests and rotations are given.
Conclusion? I'm not a "daily" cleaner, but I sort of am. I don't use Everclear but once a month, and have no sourness problems. I might do a stem polish/airway ream/bowl shine every six months, pipe depending. The pipes that require a little more attention are typically my cobs, because I notice they are more susceptible to performance issues, and I want to keep them going for as long as possible.
:shrug: