Here’s my trick: multiple sets, layer the fitted sheets, at least four, on the bed, one on top of the other. I go a month without having to put on a fresh fitted sheet - I just take the top one off and use the next one. At the end of a month, I put them all back on. I developed this method because I often get home from my second job late and find my dog has made a nest for herself on my bed by unmaking it (pulling down the comforter and top sheet) and curling up in “my spot” getting it filthy in the process. This way, I’m not fully remaking my bed when all I want to do is collapse in it!