We had one of the early versions on our last boat, with a flush/dry valve that had to be turned several turns (rather than the 90 deg turn of the current style).. What failed on ours was the plastic bits in the pump handle linkage. We had that boat 12 years and that was the only issue, aside from periodic servicing. We had a SS replacement fabricated..it's likely still going strong.
We have the same (newer) head on our current boat, and it's been very good too.
I remember inquiring with Raritan about replacing that old-style pump body with the newer flush valve, no problem, but it was $250 (15 years ago) so we kept turning the valve
The newer model also has a bleeder fitting on the pump, we've had to replace that since it was inconveniently 'squirting' onto your foot during the pumping action.