For most purposes, unless the trip is extended, I'd opt for four. In general, I find the demands of travel co-opt the time for smoking, so I'm lucky to have time to go outside the hotel or to some other sanctioned location for a smoke. I want enough to have a rotation for smoking once or even twice a day, and also a few options for which pipe will satisfy the moment. I would always take enough tobacco and not depend on finding any along the way, two or three pouches or fold-ups, different blends. And the usual one or two pipe tools, pipe cleaners, matches/lighter, and a rag for buffing. Despite having a nice leather pipe pouch, I usually opt for an old nylon shaving kit that seems to only tempt theft of deodorant and dental floss. I most often take a cob or two, and a briar or three.