Apparently adolescence is getting longer with people not taking on an adult life to they get past 25 sometimes. Umpteen years in college, bad economy keeps you living with parents etc..
True, but biologically everything remains the same development wise. Hormones don't care about the economy. And an adult life can be subjective I think.
Having Janeway entering the bridge once with a hangover because she has been helping Seven become more human by talking her into a drinking contest doesn't make her any less adult. I'm sure Tuvok would notice and show his disapproval by slightly raising an eyebrow because it is unprofessional behavior. Doc will probably have something less than flattering to say about it, but to say that Janeway reverted back to adolescence...
On the other hand, if it would be Tom or Harry who entered the bridge with a hangover, then we can moan and whine all we want about them still being stuck in their late teens.
The stuff you can get away with if you can at least fake some professional behavior for a couple of years is interesting.