Fitted pad on the mattress, fitted "contour" sheet which is the sheet on which I lie.
During the winter, above me there are two sheets and a blanket in the middle but in the summer, it is just the 2 sheets. There is a ceiling fan on low in the winter and high in the summer to keep the air stirred up.
Unless I do something to get particularly dirty in the winter, those 3 sheets only get washed monthly. They don't need washing more than that as I'm the only one in the house.
When I do the laundry, AI usually do the mattress pad and contour sheet in one load and the 2 upper sheets and pillow cases in a second load.
Because my bedroom is on the south side of the house and the tree that used to shade it had to come down last fall, this summer may be a bit more uncomfortable. It is that summer heat and humidity that sometimes requires the sheets to be washed twice a week. Otherwise, they only get washed weekly.