A shallow chamber will last me less than 5 minutes unless I'm smoking a flake. However, I put up with that to smoke my Rhodesians.For me approximately .85” wide x 1.25” deep is perfection (for English blends, which is overwhelmingly what I smoke). Most Rhodesians are in that ballpark. My tongue gets fatigued after much more than an hour, so I like a shallow chamber.
I just measured the pipes I smoke most often and this would be the size I prefer.Around 0.75" inside bowl diameter and 1.5" deep.