For most people, washing sheets once a week is the right rhythm. Over a week of nights, sheets collect sweat, body oils, dead skin, and everyday dust. A weekly wash keeps the bed feeling fresh and your fabric in good shape without overdoing it.
Some situations call for more frequent washing, roughly every three to four days. If you sweat heavily at night, share the bed with a pet, go to sleep without showering after a workout, or simply prefer the feel of very fresh linens, shorten the interval. Hot, humid seasons are another reason to wash more often, since fabric holds moisture longer.
You can stretch to every other week only if you sleep alone, shower before bed, and keep pets off the mattress, and even then, the bed will feel noticeably less fresh by the end. Going much longer than two weeks is where things tip from 'a bit stale' to genuinely worth avoiding.
A few habits make weekly washing easier and kinder to the fabric. Wash on a warm, not hot, cycle to protect the fibers, use a gentle detergent, and skip fabric softener, which can coat fibers and reduce breathability over time. Pull sheets from the dryer slightly early and finish on the bed to cut down on wrinkles.
If keeping up with a weekly wash is hard, owning two sets makes the whole thing painless: strip, remake immediately with the spare, and wash the first set whenever it is convenient. It is the single best upgrade to your laundry routine.