The way you launder your sheets affects how they feel and how long they last as much as the quality you bought. A good set treated carelessly will pill and thin within a year; the same set treated well can stay soft for many. The good news is that proper care is mostly about doing less, not more.
Wash on a gentle or normal cycle in warm rather than hot water. Hot water can break down fibers and fade color over time, while warm water cleans effectively without the wear. Wash sheets separately from rough items like towels and zippers, which abrade the fabric, and avoid overloading the machine so the sheets have room to move and rinse clean.
Use a mild detergent and use less than you think. Excess detergent leaves residue that stiffens fabric and dulls color. Skip fabric softener entirely; it coats fibers, reduces breathability, and over time makes sheets feel waxy rather than soft. If you want extra softness, a small amount of white vinegar in the rinse does the job without buildup.
Dry on low heat and remove the sheets while they are still very slightly damp. High dryer heat is the leading cause of premature wear and shrinkage. Pulling them out a touch early and smoothing them onto the bed reduces both wrinkling and heat damage. Line drying is even gentler if you have the space.
Store sheets somewhere cool, dry, and dark, ideally folded loosely rather than packed tight. Rotating between two or three sets spreads the wear and means no single set ages faster than the rest. With those habits, a well-made set will reward you for years.