It's been many years since I have had to think about resting my pipes. I smoke moderately, a bowl a day and some days off, with admittedly some weekends when I'll puff three or four bowls in a day. At some point, I entered the pipe acquisition disorder vortex and now my pipes get months of rest, to keep the rotation going and make sure that every pipe gets smoked every few months, which mostly they do. My dad was a dawn to bedtime pipe smoker, and never had more than one pipe in use at a time, so he rested them overnight, until they burnt out, and only smoked Granger. He was perfectly content and never seemed to have moisture or other pipe problems. I'd say a few days should rest any pipe sufficiently, but once your have twenty or more pipes in rotation, it isn't relevant.