You're not going to get more than 60 thousand miles out of a slave cylinder. You'll actually be lucky to get 30-40K. They are cheap at junkyards though, so if you have an older car, it might be worth it.
Well you can at the most expect 5/16 inch of travel out of a slave cylinder on your F150,this alos depends on the clutch conditions and if there is no leaks in the clutch cylinder.
The travel is going to be about six to nine inches depending on what kind of slave cylinder you have for your F-150. Mine is a six inch travel and it is after market.