If it is all covered with a spread while there are no guests, I think they are just as clean as in a linen closet.
BTW, When I visit overnight to baby sit at my DD's, I bring my own sheets and pillow (remove her pillows). I put my sheets over the top of hers, so it saves her having to strip the bed after I leave. I remove mine in the morning and hers are still ready to use for the next guest.
Mine are totally covered with the spread & shams. Guests sleep on them as they were clean when I put them on. I might run the spread & shams through an "air" cycle just before they arrive, depends on it the room has been open or not any time since it was last "refreshed". My guest room seldom gets opened!
"The soil is the source of life, creativity, culture and real independence." David Ben-Gurion
On similar subject and another guest issue...sometimes? Soap.
We use liquid soap in dispensers on the shower/bath walls and at the sink and the little wrapped motel types for anyone wanting bar soap. A friend uses full size bar soap, but does not want to open a new bar for each different guest visit, so she pours boiling water over the used bar to "sterilize it" before they arrive. She lets her guests know, and they are fine with it too.
I think sheets become stale smelling if they are left on a bed, or even if they are left sitting in a closet for too long. To me "too long" is more than a month.
For my guest beds, I remove the sheets, and make up the bed using just the bedspread. I store the clean sheets in my linen closet. When a guest is coming, I run the sheets through the wash and make up the bed a day or two before the guests arrive. I know this means an extra wash for the sheets but I like to offer really fresh smelling beds.
Mine are hardly used. It's by my grown kids when they visit. They all stay in the same bed each time. If its one night, the bed is made up for the next time they come. But if they are here for several nights, they get washed and the beds remade. Our guests rooms stay closed off with the vents also closed. A day or so before company arrives the rooms get opened up, dusted, vacuumed, and I turn the covers back and febreeze the beds just to freshen them, even if the sheets were washed after the last visit.there are no allergy concerns with them on using it.
I had to start keeping the guest rooms shut off because of my pets.my kids were coming. I had been running around like crazy trying to get ready .Thought I was all finished. A few hours before they were due to arrive, I went in one room and found the bed covered in cat hair. Apparently a couple of them had been going in there for solitary naps. So at the last minute I was stripping the bed and even washing the comforter. So all the doors stay closed now.
The guest room bed is made up with sheets and coverlet, but the sleeping pillows and pillow cases are kept containers to keep them dust-free. I have guests regularly and the sheets are changed after each visit, so I don't worry about the sheets getting stale.
I don't offer bar soap to guests, only shower gel and liquid hand soap.