How many miles do disc brake pads typically last on a vehicle? Figure heavy driving in town, with lots of stop and go.

I'm curious because one of my trucks with over 200K miles now, has had 4 sets (needing a 5th soon) of front pads while the rears are still in spec. I know the front brakes are worked harder, but it seems a little excessive. Then again, LOTS of city driving.

Thanks, Jeff

My 1953 Chevrolet
1947.1 Gallery
1972 C-10 1/2 Ton & 1972 C-30 1 Ton