NEVER dismiss a follower if you aren't at HOME
If you never dismissed a follower when you were far from HOME or somehow haven't experienced the problems with doing so then this post is for you. The problem with doing this is that the game actually makes followers run home, in other words when you dismiss someone they don't despawn once they are out of range so if you get close enough to them for zombies to spawn and attack them they may actually die because of that. It has happened to me once after I sent a character home and they died to a juggernaut after I passed them with a car. So do yourself a favor and never dismiss followers when you're not at HOME.