It is never too late, yes, and the octo- and nonagenarians' story confirms that. However, I'd suggest not to wait until that age (one might have forgotten the message by then 😀). But I completely understand if a 20- or 30-something might not have exercise for healthy aging on their radar. From a physiological viewpoint, I would say that 40 is the ideal turning point. Still young enough to dodge the chronic health issues that otherwise might hit by 60+.