Got around to finally watching AM&tW.
Was it ever explained, or even hinted at, how Janet survives 30 years without eating, drinking or breathing? Yes, of course, you can just add “quantum” to the beginning of a word and it explains everything. 
But is there an explanation?
Nope. Comic Book Physics (and Biology).
According to the director, there’s food down there.
Well, in Avengers: Endgame, we are told that time moves differently in the quantum realm. 5 years pass on Earth, but he only experiences a few hours. Their later time-travel jaunts kind of imply that you can tinker with the timeflow.
My personal opinion is that Janet spent 30 years helping the Micronauts fight Baron Karza. But Marvel no longer owns the rights to those characters, so they are not allowed to show it.
Not an explicit one, but if you pay attention to the background imagery while they’re in the quantum realm, there’s what appears to be a domed city in one shot.
Veddy intaresting!
Can’t say time runs at a different rate. because she is 30 years older.
As for your other point, she has that spear thing and a jaunty cape covering, so she must have been doing something in all that time rather than just waiting.
I guess she was breathing quantum air, and drinking quantum water. 
If you’re going to get into that, then how does “pulling time through Scott” to turn him into an old man or a baby not starve him, too?
Really, for the Ant-Man movies, you have to just accept that they work using cartoon physics, and not ask such questions. And the overall tone and visuals of the two Ant-Man movies were silly enough that that worked (I think that they even deliberately made the special effects a little bit crude, to contribute to the cartoony feel). But then they made the same nonsensical science critical to Avengers: Endgame, except that it was not at all a silly movie, and so it didn’t work at all.
I don’t mind cartoon physics in general. Doubletalk field generators and applied encarbulation are fine if they at least make an effort. But shrinking someone below the size of a quark, let alone an oxygen molecule, and no mention of how they are breathing? please!
My opinion is that the Antman movies are created for pre teens. There’s less violence, more humor, more emphasis on family. The stories are simpler (but still clever!).
If anything, I think of them for an older crowd. I appreciate Ant-Man a lot more now that I’m a dad.
Once you have the Hulk in a film, it’s all silly science.
Actually, they’ve (mostly) been doing a pretty good job on the science (even as they casually shove it into the background).
Saying Endgame didn’t work at all is a bit of an outlier opinion.
Yeah, and I think they were somewhat clever in saying, “Y’know, all the time-travel stuff from other time-travel movies is really not the way things work.” and yet they still don’t go too deep into the details of how it really works.
The discussion between Hulk/Banner and Sorcerer Supreme was coarse enough for us to get an idea of the basic difficulties and caveats, but still didn’t get deep into the supertechnicalifragilisticities. The mere fact that the Avengers’ engineering department was playing with invent-in-an-instant nano-tech armor for himself and the kid from Brooklyn gave us the leverage to just assume he could also slow down a bit and engineer controlled entry/exit from the Quantum Realm as well as carefully manipulate time-travel, as well.
–G!
