Careers are generally safe, but yeah, Discover University does not work well with rotational play. Also note that if your Sim is pregnant, and you leave the household for three days, when you come back the baby will be there - even with aging off. The baby will stay a baby, and no one else will age up, but pregnancies don’t pause.
I admit to having taken advantage of this once or twice when I just didn’t want to deal with it!
Pregnancies aren't as much of an issue. It's not really tied to aging and the only thing it doesn't let you do is pick a name, which you can change by editing the household through Household Management when they become a toddler (though will probably be possible as in infant in March when the new Infants state update drops). My Sims have Professional Slacker, so I wasn't really concerned about careers and such, but more should be put in place to favour rotational play, especially since a lot of people play many generations (there are even Trophies for 10 and 26 generations played). It's obvious the game was meant to be played this way, but it's not good when the game kicks you in the teeth for it.
Yeah, I have my unplayed households set to not age, etc. but I handle university differently for the reason you mention.
(This is what works for me, as a rotational player, and may not jive with your style.)
1. When my teens that I plan to send to Uni age up to YA, I put them in a new, not-in-world household named Foxbury Students or Britechester Students at the end of their rotation.
2. At the end of the final rotation, I place these students on a lot or in an apartment, turn aging off, and have all of them apply to Uni on an assembly line.
3. They spend the week doing Odd Jobs or working part time, raising their Research and Debate skill, and making friends with each other. I turn off aging because I prefer to have them enroll on a Friday and don't want to "charge" them days for my convenience, YMMV. (Only really an issue if you're not playing on long lifespan.)
4. I enroll them in Uni on Friday on an assembly line, enduring many loading screens to move them all into the dorm, one by one. (Optional if you don't want to mess with the dorm.) I've done this with 8 students.
5. Play University as normal, perhaps having them all in a club where the activities are be friendly and do homework. Since it's Friday, they have ALL WEEKEND to do their research papers and presentations.
6. Play through until they all graduate.
7. Split the household and have them all move back in with their parents/original household. Turn aging back on.
If you're not feeling back-to-back University 😉 you can play Britechester when the last Britechester-bound student joins the Britechester hosuehold, and Foxbury when the last Foxbury-bound student joins the Foxbury household.
That said, yes, I developed this strategy because University doesn't play nice with rotational gameplay. I used to always have my college students live at home, because that was MY university experience, but... the dorms are more convenient if you have a household of 6 students.
