Another way to look at it is, when is old, old?
Mine was built late 2007, sat for 1 1/2 years unused then started a life of 150 night, 15,000 mile plus seasons. Is it old? It has had more than average use. It has also had more than average maintenance in the parts that take the most wear. Spring hanger areas of the frame have been re engineered to be far stronger than original. This year springs were replaced, upgraded to a 7 leaf from the minimal spec 6 leaf. This year shocks were replaced. Steel wheels were replaced with blingy aluminium. Brake assembly replacement is on the 'to do' list for next spring. The fridge was replaced this year.
So, how old is old? Lots of us have various bits & pieces of replacement parts in our bodies. Hmmmmmm.