How often do you wash your sheets and put fresh ones on your bed? That’s OK, you don’t need to let anyone else know; you can keep the answer to yourself. However, the best answer is no longer than two weeks, and less in some cases.
If you and your family are sleeping on sheets that have been on your bed longer than that, then there are some gross and unhealthy things that may be happening in your bedrooms. So be prepared: What follows may not be for the faint of heart.