Hard to say and I am still a newby at the AS thing. But, one thing I have seen in my short life and I tend to find fits most occassions is that the older something is, the longer it will last with regular maintenance. As industry grew in general, companies figured out that making it to last longer wasn't profitable (not saying AS here, just an observation on industry in general).
I currently have a 1979 AS. The plastics that were inside were cracking and I wasn't a fan of the sticker woodgrain. But the shell, frame, stove, fridge, AC, heater, etc. were all in perfect working order, mind you some cosmetic issues. I would bet that many of the 1950's AS appliances still work (if the owners didn't want upgrades for cosmetic/safety reasons) and with a little cleanup, look as good as new.
I would be surprised if a year 2000 model AC, stove or fridge will still in working order in 2030. At the rate things are going, something large like that bought today barely out-lasts the warranty of 1-3 years.
Tadd, Beth, Grundgetta and Weeble
Proud to be Air #37137