I'm a fast smoker, whether it's my pipes or a cigar. Very few cigars break an hour for me. The few that do, I usually give up on em at that point because I have something else to be doing.
I pretty much smoke cobs exclusively, got a few briars but they're too much work and all smoke wet n hot. My largest cobs, when I light as im leaving work, will get me another 20 minutes in my chair at home, about 45 minutes on average for a country gentleman. My smallest cobs im done before I get home, around 15-20 minutes.
I pretty much only smoke flake, and only 3 kinds. Ennerdale, DFM, and LNF. I do have one DG briar that does very well with CH, and that's usually a 20 minute smoke. Sometimes I'll load something different in a cob, and not being a regular, I get varied smoking time.
Like others said, there's more than just bowl size to the length of the smoke. Moisture, cut, pack, bowl material, puffing habit, and blend all contribute. Also, not all bowls will smoke all blends. Since I mostly smoke cobs, most of mine are dedicated to a blend they smoke well.