Most moisture is from condensation from the combustion of tobacco, but clenching (leaving the pipe
in your mouth/teeth) probably contributes some saliva and some moisture from exhaling into the stem
a little. Packing the pipe right helps; see the video on this at pipesmagazine home page. Tamping may
help a little, by keeping the burning ash a little tighter and drying out the moisture. The cobs have an
area under where the shank enters the bowl that traps a little moisture and keeps it from gurgling. Dryer
tobacco may help. Play around with these variables. Gurgling is really annoying and spoils the spell of
a good smoke, but in most cases it does no harm, doesn't put out the leaf nor deliver a mouth full of
moisture. The pipe cleaner trick is a good one. On resting pipes, I think a good 24 hours between bowls
is best. Some of the old timers, like my dad, chain smoked all day and into the night, and never smoked
but one pipe until it cracked. These guys laughed if you mentioned resting a pipe. They didn't rest, why
should the pipe? I'd have enough pipes to have one for every day of the week you smoke, or more if you
have multiple bowls a day. A bunch of cobs do great. Most of us accumulate enough briars over time.