There has been much debate about how often we should change our bedding! Household experts (Apartment Therapy), have some pretty good guidance for us.
Sheets. You sleep on them every night. You sweat, your oils, your skin end up on these sheets. We spend 1/3 of our lives in bed! If you sleep with an animal, all their dander (even fecal matter), hair and skin end up on the sheets. Wash these things AT LEAST once per week.
Your comforter. If you don't have a duvet cover, you should wash once per month, at least. Again, every night, sweat, skin, oil, etc.... If you have a duvet cover, wash the comforter a few times a year and the duvet cover monthly.
How about those decorative pillows? At least once per year!
I've got some washing to do, how about you?