what Mainevent said is basically right. lower rpms = less heat from friction. the faster the rpms go the more heat the clutch will make when you are engaging it. heat + not fully engaged clutch = fast wear.
best thing to do is learn your gears. learn how much of an rpm change there is between the next gear up at a certain speed.
for example say im in 1st and shift at 15mph, i know my rpm is going to go from 3.5k to around 2k. but at 50mph 4th to 5th will go 3krpm to about 2.2k. once you get the hang of that all your doing is: clutch in, shift, wait for where the rpms should be, then let up the clutch easy but still fast. if you are matching the rpms right it shouldnt matter if you feather the clutch or just side step the pedal, it should be pretty much in sinc so minimal slippage.
you dont have to get it perfect, but just get it in the genral area. and keep the rpms low. doin that i dont doubt you can take a clutch 150k miles. but who the hell wants to drive like an old granny??!?!
