I use sheets all the time, cotton and flannel. Some of the sheets are poly/cotton and they work too. I look for sheets on sale and my small local department store (Giant Tiger in Canada) often has flat sheets that are seconds for less than $10 and even some of the main brands made in the U.S.A. which make great long wearing backs. I try to buy King sized sheets and use any extra fabric to make matching pillowcases which can be used to store the quilt when it isn't on the bed. One look at the pillowcased quilt sitting on the shelf, tells me what quilt is folded inside without pulling my linen closet apart.