From the Learmount/BBC Q&A:
They can keep flying until they are 65, but there is a rule that if one pilot is between 60 and 65 the other pilot has to be younger than 60.
Were I writing the rules, I would
require that one pilot be over 60.
The yet-unanswered question: If a deadheading pilot is called up to fill an empty seat, is he exempt from out-of-hours rules? Does he collect overtime pay? Who pays for the lawyers?