Nitori Duvet Cover - N-Grip Yona Size: Queen Used for 1 year. While there are no noticeable stains, there is some dullness, wear and tear, and small pills. I think bleaching with sodium percarbonate, etc., would be good m(__)m Although I am a layman, as far as I can see, there are no loose threads, so I think there are no problems with use. It has been washed, but it was about half a year ago m(__)m Thank you!