Unbleached and undyed cotton is more fragile than it looks — not physically, but chemically. Without synthetic coatings, the fiber can only stay soft if you let it breathe.
Wash cool, dry low
Heat is the enemy of every natural fiber. A 30°C wash and a low tumble cycle will keep fibers springy far longer than hot cycles that cook them stiff.
Skip the softener
Fabric softener coats fibers in wax, which makes cotton feel smooth for one wear and papery forever after. A half cup of white vinegar in the rinse does the same job and rinses clean.
Wash on a rhythm, not on reflex
Sheets every one to two weeks, covers monthly, quilts quarterly. Washing less often, more gently, beats washing constantly. Your linens — and your water bill — will notice the difference.