At what point do they decide to call it quits? As someone mentioned this is the new world order with an ever increasing number of aging pilots. It is also unchartered territory. There are plenty of examples where the "system" has failed the industry so the mantra that "as long as they pass the checks and the medicals" suggests that those two criteria are enough to prevent incapacitation or incompetence. I have flown with some very good over 60's but I have flown with more who are hard work and demonstrate that age does indeed weary.