I have one filtered MM cob and a Dr. Grabow. All my other pipes are unfiltered, even my Savenellis -- an Oscar Lucite prince, a
churchwarden 601, and two unfinished pipes decades old, an elegant slim straight billiard and a 404 zulu/yacht. I would rather
smoke a milder tobacco, in general, than tame a harsh tobacco with a filter, but I occasionally do, for example, when a tobacco
gets more bite as it dries. For whatever reason, I don't seem to have a lot of moisture problems in smoking, so that isn't an issue
for me. I change my filters about every three smokes. I understand all of the 6mm filters -- balsa, Dr. Grabow, and Medico -- are
interchangeable in pipes.