Yup. I like that guideline. It’s called “1/2 +-7″ I think? First heard about it a couple years ago and it’s logical. I mean there’s definitely room for moving outside it I’m sure but for people that do, they shouldn’t be shocked if folks look at them strange.
I think you can have have friends at any age. I have friends all over the age range, usually followers from old Vine or other places. But I’m ancient and sort of parental-ish and there’s unspoken social power that I gained simply by aging that I’m fully aware of. People that take advantage of that extra power get no respect from me.