The last place I worked had an old Bridgeport Mill about 50 years old that nobody used because the table was so loose. It had a good, variable speed head that ran smooth, a good brake, power feed on the X axis and a digital readout. I cleaned it up, adjusted the gibs and the split screw and used it daily for 8 years.
It's fairly hard to wear out the body of a good quality knee mill. The head will sometimes need work,..usually the spindle bearings. But the ways on a milling machine will last longer than the person operating it if they're kept clean and oiled.
