Depends. I have an accuute sense of smell. Before it smells bad, it stops “smelling nice” usually a 3-4 day grace period. In that range, I wash them. It varies because in winter, the heat register dries them pretty fast, in summer, less so, but the HVAC fan constantly circulates so since they dry fast, they keep longer.

In the summer, I’ll do less than a week sometimes because I’ll shower more than once a day because sweat. They stay wet longer and get “unfresh” faster.