Years ago I hunted with a group of 5 other guys. We would take stands and do drives. I saw more than one hangfire and even mis-fires (caps only) that were the result of a guy shooting his gun, reloading, and then keeping that load in for a few days before shooting again. The fouling and primer residue from the first shot sucks moisture out of the air, just like BP or Pyrodex will.

For those that hunt with fouled bores, I would say discharge and clean every day.