My LR3 is still using it's original air struts and I'm at 250k miles. The ride is not as cushy as my LR4 but still very good.For the serviced struts, I would expect longevity issues vs new, but they may be fine too. I'd be interested in hearing back on how they do, I don't have first hand experience.
I hear the Land Rover brand struts can last a long time and that is what I'm getting if the time ever comes. They look very strong, well built like they didn't f around and made them to last. I've got 115k mi now and as long as I don't jump it or do something stupid then I'm hoping to get 50-100k more out of them.