The only time I've ever unfriended people is if I see they've deactivated their account.
That, or, sometimes I'll accept friend requests from people I don't know, but they clearly are fellow puppeteers wanting to network with other puppeteers, but after a while, I'll have forgotten I accepted their friend requests, and since I don't really know them, and/or have hardly interacted with them at all, then I'll eventually unfriend.