I have a utility trailer that was built in 1950 using car front axle spindles and bearings from a 1937 Plymouth. I serviced the bearings for the first time (complete washout and re-greased) in 1982. They are still going without further attention. 32 years the first time, 33 years and counting now.

I've serviced bicycle bearings that ran 30 years after servicing with Campagnolo grease. A little bit icky but not too bad.