I think 70 years is a not unrealistic timeframe. Think about 70 year old watches. A 1950s Rolex for example, with its hand done lume, its thin, stretchy bracelet etc. I'd argue the tolerances involved in making lots of the parts today, with the latest, greatest, computer controlled CNC machines are smaller than Rolex's manufacturing tolerances in the 1950s. So with servicing, the replacing of failed parts as and when they fail, just like a 50s Rolex, modern reps could easily be alive and kicking in 2090. They're just a lump of steel at the end of the day.