I took my 26 year old, 450,000km Bosch unit to my local autospark. I wanted it re-built but he wanted to sell me a new one. The new Bosch unit was about $50 cheaper than the re-build.
I asked him how long my own unit would last if rebuilt and he said probably as long as it did the first time. He wasn't particularly confident about the longevity of the new units. He thought I was mad paying extra for the rebuild, but when I explained how long I expected to keep the car for and how often I'd be way out in the middle of nowhere, he changed his mind.
New diodes, slip rings & bearings and it should last longer than the car.
I have a problem with the bulk re-manufacturers who sell through chain stores, so I always seek out the old-school tradesman who will do the rebuild for me. Costs more, but I've universally had better service and better results.
Support your *local* tradie!