Lumley, Sawchuk, Vachon to a certain extent & others who have followed were "phenom's", as its rare for a Goaltender to be able to immediately make the transitions from level to level, those that do often burning out after one, three or five seasons. Amongst certain enlightened amateur & Junior organizations, NHL clubs "back in the day", rather than rushing a kid up, they'd slowly do so, whereby even if he was capable of playing Jr.A he'd be assigned to the Jr.B club, groomed & tutored, a handful of call-ups followed by a year or 2 at the 'A' level, an apprenticeship in the Minors (which in a lot of cases, Johnny Bower for example) wound up being like, forever.
It takes an astute combination of Management, Scouting & Coaching, handling, in catching and relying upon a shooting star, many of whom can be "difficult" (Sawchuk) and inconsistent. The mark of the truly great ones is in their ability to adapt & change their game up. No one in the history of the position did that better than Jacques Plante, Brodeur, Hasek & Tim Thomas enlightened & studious enough to follow suit who through reinvention & hard work in practice were able to achieve what they did/have. In many respects Hasek & Thomas (but 2 examples) real throwback's as they came up through tier's, understudying, sustaining their peaks through change, innovation, adaptation, peaking at later ages.