I might be ignorant of all the limiting factors, but the average lifespan of a passenger railcar in the US has been about 50 years. VIA has squeezed even more out of the all-stainless Budd cars they inherited from Canadian Pacific, albeit their operations are on a vastly smaller scale and some US commuter operators have also strung along for longer than 50 years. The time span from the entry into service of the Superliner Is (1980) plus 50 years takes us to 2030 so it seems reasonable to me to expect to be able to get them to hang on that long. Superliner IIs can be expected theoretically to be good until at least 2041. I expect to see Superliner I's being subject to increasing cannibalization, and perhaps some creative stopgaps such as Horizons and perhaps even Amfleets being pressed into long-distance service. Gardiner seems to have been communicating the expectation upper management has, whether it is realistic or not is something I'm not qualified to answer.