I have a pipe going nearly constantly. More likely than not, at any given moment I'm somewhere puffing away.
So it's hard to keep count, but I'll guess 7 to 9 bowls a day.
Two points though:
(1) I smoke a lot of P.A., which is so mild-flavored it doesn't wear me out;
(2) most of my pipes are group 3 sized (medium-to-small) because I seem to lack whatever skills it takes to nurse a large bowl of tobac to the bottom. I can't seem to get good re-lights on those deep bowls, but shallow bowls, even the large ones, work fine.
That's one of the reasons I'm almost always smoking bulldogs. (The other reasons are I'm in love with the looks and feel of the shape; and I think it compliments my appearance.)