How many sets of bedding per bed
Short answer: Two sets per bed is the minimum, three is comfortable. With three you can change without having to wash the same day.
Why two is the minimum
With two sets you put a clean one on while the used one is washed. That works, but it means you have to wash on the day you change. With three sets that requirement disappears.
Three sets in practice
One on the bed, one clean in the cupboard and one in the wash or drying. That is the rhythm that makes changing the bed something you never have to plan. See bamboo bedding.
Extra pillowcases
Pillowcases should be changed more often than the rest, because your face rests against them. Having two or three extra cases makes that easy without changing the whole set. See bamboo pillowcases and bamboo sheets.
Frequently asked questions
How often should bedding be changed
Every week or every other week. More often if you sweat or sleep without nightwear.
Should the guest bed have its own set
Yes, at least one. Two makes it easier if guests come two weekends in a row.
How long does a set of bedding last
Three to five years with ordinary use and washing at forty degrees.