I see what you are asking now !
I will give a few examples just for comparison.
I bought a 1977 K-10 from a friend of mine that had 160,000 plus miles on the original clutch. It was a diaphram style 11-7/8" diameter and was driven very sainly most all of its life. The truck had 3.08 gears with 31" tall tires.
I had a 1969 C-10 with a 11-7/8" three finger pressure plate that had well over a 100,000 on the odometer with the original clutch . The truck had 3.73 gears with 28" tall tires.
I drove a wrecker ( tow truck ) that was ABUSED on a daily basis and it would go through diaphram clutches about once a year and Borg and Beck style about every two to three years. The truck had 4.56 gears with around a 32" diameter tall tire.
On my 83 K-3500 I had a 11-7/8" diaphram clutch and it did not last long at all with heavy skinny pedal usage . I replaced it with a cheap name brand three finger style and it lasted for a fairly long while ( can't really give a mileage on that truck since it was a play toy ) and it was abused every single time it was run.
That same clutch went into my buddy John's ( NVRENUF ) truck behind a STRONG roller BBC and it lasted a long while but we replaced the disc with a ceramic unit . It ended up slipping towards the end but I do not blame the clutch - John would let some crazy guy drive his truck from time to time and I believe it was abused each and every time....
We have also had absolute reliabilty out of an after market dual disc three finger set up by McLoed even though the abuse was very high.
NVERENUF had a nice BBC and a ceramic disc three finger clutch in his K-10 for years and years nad years with 38" tall tires with 4.10 gears . He used a whole lot of skinny pedal on a regular basis. The clutch came out of his truck ( he decided to turn gay and put a TH400 in his truck

) and went into another BBC equiped K-10 with 3.73 gears and 39.5" tall tires . That truck ran that clutch for years until it finally started to slip under load . That guy replace it with a cheap diaphram clucth and it did not hold up what so ever under any kind of abuse.
Sorry I can not give you better mileage figures but the play toy applications were not driven everyday and most trucks with 40" and 44" tall tires speedo's are not correct anyway......
These are the best examples I can remember that might help you out .
HTH's Tom