How do bike years compare to people years?

We went by Brompton to Lorsch to a rally about the line of the new high speed railway line from Frankfurt to Mannheim. The plan is to run the line east and parallel to the A67 autobahn through a forest. In addition Deutsche Bahn plans to run goods (freight) trains along the line overnight. Many locals object to this project because of the damage to the local woods which are an important leisure area and because of fears about health problems due to noise pollution. There is a serious suggestion to submerge much of the route in a tunnel. We understand these fears, but also support any move to move goods transport away from roads to rail.
While we there we met various friends who are members of the ADFC (German Cycling Club), chatted to the odd soul on the stands, enjoyed Kaffee und Kuchen (coffee and cake) and listened to an excellent local amateur big band. It was a fairly typical summer afternoon in Lorsch. We set off for home and in the Viernheim Woods Judith got a stick caught in the chain tensioner. The chain left the pulley cogs and the drive train jammed. We had no choice but to turn the bike over, loosen the chain tensioner and get oily. We had almost finished when two of our ADFC friends appeared and enjoyed a little Schadenfreude. One of our famous Bromptons was giving us problems. We pointed out that the bikes were twenty years old. Then came the question, "How old is that in people years?". This we couldn't answer, but it struck us that if the Bromptons were cars, and both are about twenty years old, they would more than likely be sitting on a scrap heap rather than being ridden about.