Pillow protectors every time - dribble, snot etc.
The mattress protectors are washed almost every time but if I’m in a crazy hurry, I might leave them until next time unless I can see that it has been marked in some way.
It depends too how long the stay has been. I only skip the mattress protector if the stay has been one or two nights (and usually a solo guest). Any longer and it’s going to get washed no matter how much of a hurry I’m in.
Our two apartments both have the same size beds so I have adequate spares of everything on hand.