...when the adult Sims travel away from it.
I have a household with two adults and one child Sim that own a couple of retail businesses. Usually I travel to their businesses with one or other of the adult Sims and leave the kid at home with the other parent, but I thought I'd try something different with the new nanny service. So I had them hire a nanny, he arrived soon after and introduced himself. The kid seemed to like him and was having fun so the two adults travelled to their bakery business. For a while I forgot about the kid at home until there was a knock on the shop door and the nanny introduced himself!
I was baffled, but as there are still unresolved bugs with the bakery venues I didn't really take much notice. The nanny kept wandering around cleaning up dirty dishes though it became irritating when he kept saying stuff like it had been a long time since they'd met, or something like that because it hadn't - but I've long since given up questioning Sim logic!
Eventually playing the bakery became too much like hard work so I closed it, all the customers left but the nanny stayed hanging around. Then I had the two adult Sims travel back to the home lot and the nanny was there, he said the same "it's been a long time since we've met" which again wasn't true, and then there was a notification that his time was up and he left.
I've played a different household where they called in a nanny and none of the adults travelled away and I like the way the nanny interacts with the family as a whole, I also like the way they can be paid for the time they've spent with the family, or that you can have them for the full 24 hours. But, what I didn't like (and it's probably a different issue) was that the first thing they did upon entering the house was spray anti-monster deterrent under all the kids' beds. In my game I've never seen the monster under the bed, I don't have any of the wall lights that prevent the monster, and every morning the kids wake in a state of panic. I've even seen the kids talking to their beds, presumably to the invisible monster lurking somewhere beneath. I am sure it's by design as the nanny's job is to care and protect but it still bugged me, I think it would have been so much better if the kids were able to ask adult Sims (nanny too) to spray for them, or leave well alone for the sake of fun gameplay.