In reply to Game of Conkers: I actually agree with this...
Working in ageing research I get to talk a lot to those studying centenarians.. they look at the traits/activities/genetics etc.. and when I ask about their training load they laugh..
and tell me.. forget it.. all you marathon runners are dead long before 100.. in fact one said the very trait they don't see is they rarely see centenarians who have been endurance athletes..
But there are worse things for the body, so if I'm too have an addiction its not a bad one to have and I lead a great life..