About Discover University

In the sims 4 time will continue back home. University is not a completely separate environment like it was in the sims 2. Sims in your other households will age up while you are away. 

The amount of time it takes to graduate depends on the number of classes you take each semester (one semester is one week). You need to take 12 classes. The fastest would be 4 courses each week, so 3 weeks. But that's a lot of work, your students will be spending almost all their time studying. I usually go for 4 weeks with 3 classes each week to spread the workload, but that's personal preference. So keep in mind that the sims at home will at least be 3 weeks older. 

Rotating between households during a semester is tricky. You risk failure at university if your students don't study enough or if you are playing another family during graduation. 

If you don't want the family at home to age while your student is away in a dorm, you can temporarily turn off aging in the settings. 3 or 4 weeks can be a lot of aging if you have younger sims in the household. For example you could allow the family at home to age one week to simulate progress of time and then turn it off until your student comes home. 

In sims 4 sims living in a dorm is totally optional. Your sims can stay at home and enrol in university. They will commute to uni. That way you can play the entire family.