True, it's fair to say that we do all age at different rates - but it's also fair to say that statistically, people these days are not only living nominally longer, but are healthier longer as well. This has been happening over a period of years - in the Christie case, over Capt Christie's career the max age was moved from 55 to 60.
Lifestyle, genetics and a host of other factors doubtless play a part. The captain of the Iberia A340 which recently had to drop into Lisbon was doubtless within age and checked out fine at his last medical.
That didn't prevent him from later suffering a fatal heart attack.