Some of the R68(a)s aren't even 25 years old. The nominal lifespan of any train car is about 40 years at the least, so barring an unforeseen occurrence like the R44s, the R68(a)s aren't going anywhere anytime soon. When we get closer to their retirement, sometime in the late 2020s at the earliest, we can talk about which cars are museum-worthy. More @Wikipedia
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