Surely the tradeoff here is that, provided a company treats you okay, you're more likely to stick around than that colleague (if he's that driven then he's sure

Surely the tradeoff here is that, provided a company treats you okay, you're more likely to stick around than that colleague (if he's that driven then he's surely constantly looking for new opportunities?) and an employee with a few years knowledge of the codebase is generally worth a lot more than a super skilled newbie. Depends on the area though, I guess. Video game companies seem to have a preference for working people into the ground.