If your clutch is going out at 55k, you are a worthless driver..lol, im serious.
Even if you "beat" on our cars, I could imagine the clutch lasting an average of 150k miles...
I have no clue what kind of shifting your friend was doing. He should sell the manual teg and get an automatic if he shifts that poorly.
The thing to worry about is speed of clutch engagement/disengagement, and the duration of that movement. Not to mention you have to be shifting it correctly. All those misshifts or grinds arent good for either clutch or transmission (poor synchros!).
Id say 150k then switch it, its old, lol new clutch= more power anyways.
Im at about 137k, ill change mine when I build up the engine...Clutchmaster FX300 baby!
Lates!