A good rule of thumb when remembering how many sets of sheets you should have is... 2,yep that's it. 2 sets per bed in your home. That is one set on the bed and one to change out when it's time to wash the bedding.
Another tip is when you are crunched for storage space,fold the extra set of sheets and tuck them neatly between the mattress and box spring. Then on laundry day all you will have to do is take the sheets out from under that mattress and put it on them on the bed(s). Wash the dirty set(s) and then fold them and place them in between the mattresses.
The Happy Homemaker