I cannot confirm for sure, but I feel that way too. It seems entirely random, at best - being a time traveler too, I had a villager move out after 3 days, and some that have been around for like 10+ days. I only talk to 3 of my villagers that I intend to keep and generally ignore the rest, but that doesn't seem to be a factor - one of the villagers I talk to daily asked to move out once, and then villagers I don't talk to took way longer to move out. Just seems random to me, as far as I can tell.
And yeah, I've only seen two campers so far, if I can even count the first one since everyone gets a camper immediately after the campsite is built. I think you can only get a camper if you have a free slot in town? Not sure if that's true or not, but seems that way for my town. And my plots don't stay open for very long, so I'm thinking that might be why.