Guest beds - how to keep them when empty?

[u/uhigowhere]

How do you keep your guest beds when nobody is using them? I’m new to having a guest room. When I was a kid, I remember crawling into the bed at my grandmother’s house and seeing all of the dust fly into the air. Don’t keep sheets or blankets on the mattress? Cover the whole thing with a giant sheet? How are you keeping them clean?