Toddlers - do you level them to level 3 or level 5 before aging them up?

I mostly play on Long now, so it’s plenty of time to get all level 5 skills, particularly since I have the Education Overhaul mod which helps raise skills when toddlers are at preschool. I’ve never had them get to level 5 on Normal with all of the skills, usually Movement and maybe one other. I do usually manage to get level 3, though. One thing I have noticed is that you don’t actually have to max out the Potty skill, although it is useful to get it to level 2 so they can go on their own (if they don’t have the Independent trait).