What is your Gamechanger feature?

Being able to control aging during my rotational play is a huge game changer for me. I have it set up like I did in Sims 2 where the active household ages when I play them. I also love the ability to be able to age townies with a check mark. I delete many of them but the ones I keep around, I like them to age with the current generation.

One thing I wish I could do which was my favorite feature from Sims 3 is set how long I want a sim to be in a certain age. For instance, the ability to say I want the babies to age up at 3 days, toddlers at 7 days, etc...