Well, it may be true that people who dare as little kids might do more inappropriate stuff in their teen years, but only if they are still dating by then. Especially if they have lasted together from toddler age to their teen years. I mean, toddler dating after all is pretty innocent thing, but I would say definitely don’t start getting worried until they start entering their pre-teen years. If I had children who began dating in their toddler years, I would try to ensure that they don’t hear about sexual relationship, and definitely no sleepover together either, because they will probably start enjoying their time together even more and will want to go in even more sleepovers. Though it starts out as pretty innocent, it will likely no longer be innocent by their pre-teen years, so definitely no sleepovers so they won’t want even more of those. Of course, many can argue that the relationship will no longer be too innocent by their teen years if it lasts that long, and so when they are entering their pre-teen years, before getting involved in inappropriate things, it is best for their parents to talk to them about what they will probably start hearing in school and to not imitate it, nor to get involved in those conversations with anyone else, including their significant other, so they won’t slip into becoming teen parents nor doing stuff they shouldn’t, because if it did last into their teen years, it seems like the chances of becoming teen parents have skyrocketed and gone astronomical if not supervised by their parents. As long as supervised by then and not like being bossy but being an effective counselor/advicer will help minimize the chances of them becoming part of the typical statistics.