Ageing depends on number of charge/discharge cycles, depth of discharge, extension of charge, temperatures, speed of charge and a few others. Add manufacturing tolerances.
It is not a one dimensional problem, and it is dealt with or not in different way by manufacturers and users alike.
Edit: It is worth noting that manufacturers are penalized by reviewers for practises that prolong battery life, such as not overcharging and deep discharging (giving the impression of worse battery life), and not charging at very high rates which typically also gives lower life time both through chemical mechanisms and heat (but of course gives faster charging).
Battery longevity does not lend itself to easy testing, so all respect to manufacturers that still act in the best interest of their customers.