I've noticed I can finish off a bowl of C&D Big N' Burley in a MM Diplomat 5th Ave. in like 15-25 minutes. Something about the thin ribbons, dryness and burley content make that stuff burn fast as hell no matter how tight I pack it. That's not exactly a bug, though. It is easy to light, stays cool, requires very little attention and tastes very pleasant. Very nice for the car.
I rub out all my flakes, plugs, ropes and coins. I find that Gawith (both houses) flakes burn extremely slowly for me. A medium sized billiard bowl of Dark FLake U/S can last me up to 90 minutes, and I'm not much of a sipper. Usually at least 70 minutes. C&D-made flakes also last a long time for me. So I guess my answer is thick, meaty flakes.