If proper care is given to duvets and pillows the rule of thumb is 5-10 years for synthetics and 10-15 years for naturals. Pillows tend not to last as long because they are subject to more wear and tear than duvets as you sleep on the pillow and under the duvet, therefore this would apply to feather beds also.
Proper care would involve the following:
- Regular airing of duvets (new duvets for 24 hours before use)
- Shake the duvet now and again to fill it with air and maximise its loft
- Fluff the pillow every now and then to maximise loft
- Use a duvet cover to protect the duvet
- Do not wash on a regular basis as the duvet cover acts as protection. Local soiling should be hand washed and more serious soiling to be addressed in large commercial machines only
- Do not dry clean