"However surely 70 year old planes belong in a museum".????
Why???
If the airframes are sound and the engines and systems appropriately maintained why on earth would they need to be in a museum for goodness sake? These are solidly built and over-engineered beasts and far more confidence-inspiring than many modern aircraft. I would prefer to be in a DC3 in ice than say an ATR42/72 with it's tiny little wing.
Have a look at say a Tecnam (where rivets join lightweight metal and plastic!) and then wander over and look at the construction of a DC3. Even Boeings and Airbuses have such short lifetimes nowadays. 777's are being scrapped and 7 and 8 year-old 737's and A319's are ending up as saucepans whereas the venerable DC3 just keeps on keeping on.
I think they'll outlast most of us and will certainly still be flying on the 100th anniversary of their first flight - simply outstanding.