Filters are a matter of personal preference. Mostly I don't use them. If you use the 9 mm filter, I think the recommended use is about three or four bowls, which I think people probably use them for a dozen or twenty. Other options including just removing the filter for an open draw, or if you prefer a more focused airway, an adaptor provides a no-filter airway that is a little more narrow. Filters are not described or explained often enough, unless you have a really good pipe shop proprietor at your disposal. Most of us learn by trial and error, and people buy filter pipes without knowing the filters are there, and without any plan regarding them, so you are not alone. The use of filters, to me, is if you want to somewhat mute really strong tobacco, or if you are going to smoke much more than usual, as at a pipe show or pipe club, to keep from getting too much nicotine or tongue bite. Other filters or similar devices include 6 mm, balsa inserts, Brigham maplewood inserts, and various adaptors to smoke filter pipes as non-filter pipes, and many old fashioned stingers, not really filters, but moister condensers. Learn enough about these to know whether to avoid, adapt, or utilize.