Had one replaced in my 1979 $825.00 But I didn't have to lift a finger.
It is like a light bulb, if you baby it, it could last 10 sec. or 10 years. I would guess closer to the 10 sec. mark. Plus you can cause more damage.
Get it fixed! It is a pane when you have to push them.
 Heard a slight knock comming from my 10 bolt 4x4 rear end so I took the
 cover off........oops. Pinion gear has lost a tooth and the tooth fairy
 did'nt show up but now I need a rear end or at least a gear set. Any one in
 southern Ontario have a 373 10 Bolt lying around with 6 bolt axles or a gear
 set for this thing? Been driving it for 2 weeks with this tick b4 I took it
 apart , how long do ya think it would last if I baby it? hard to find parts
 in such short notice ya know.

 Thanks Dave.