Probably not pressurized ones. Pressurization limits an airframe's longevity whereas aircraft that are not pressurized can pretty much be flown forever so long as they are maintained.
Right. Our DC-6s where pressurized originally, but when we got 'em we pulled out the cabin superchargers, mixers and all the pressurization stuff. Makes life much simpler maintenance wise. But what's really stupid is even though we don't fly them pressurized any more, we still have to certain inspections to comply with ADs dealing with pressurization issues.
Our oldest planes (C-46s) where never pressurized, and where built in the war to only last 500 hours (they figured during the war, within 500 flight hours it would either be crashed or shot down). We have some at over 30,000 hours now, but all the really poorly manufactured war-era parts have been replaced with better post war (1950s) manufactured parts.
We do however operate DC-9s, some of which are 40+ yrs old which are pressurized, the more cycles they have the more NDI stuff we have to do on the pressure vessel, but we've never encountered any problems in that area.
It's just funny to me. 24yrs old where I work would be considered practically brand new.