Well I think this is a prime candidate for the tracking thing, and honestly, for medical, at the bare minimum, I'd place it at around 100, that's 50 2 hour games, which averages on nearly two weeks of playing exclusively medical for 2 games a day. By that time you should have some understanding of the fundamentals at the very least. Maybe I'd set it even higher, a month's worth of game, maybe two. If it truly is supposed to represent experience on the job it's got to have something backing it up, instead of some rando who's played doctor for 3 days and gets a title saying he's the new Doctor House. Setting it high could also make it like a long term goal thing, so players could have something to pride themselves off of, in return of their dedication? I guess?
As to reasoning why the CMO gets a shorter time to play it, well I have absolutely 0 reasons for you, partly because I think they're too short to begin with
also other jobs probably would have different time restrictions to them, security probably could get away with a shorter one, while engineering might be a bit higher
fuk science u nerds