It’s easy as kids because you know you’re both regularly going to be physically present in the same place at the same time, so you’ll actually have a chance to do friend things. You don’t get that as an adult. You need to figure out if you can actually stay in touch with this person (e.g. maybe you have a shared hobby that allows you to regularly meet). You also have a better idea of what kind of people you get along with as you get older. With less time to spare, you definitely want to have these boxes checked before you invest more time into a relationship.