Do you need to clean a quilt that has been covered with a duvet cover all winter?

As long as there have been no big spills ( tea or coffee in bed etc.) I put mine out in the sun in the yard ( a balcony would do) for the afternoon, then shake it out and put it in the dryer on air fluff for about an hour. I worked in a dry cleaners and they used to say that although you CAN wash and dry a feather duvet yourself, it's very difficult to get the filler completely dry and it will mildew over time and become unusable. they have huge, very high heatf drum driers that really get it thoroughly dry, so if it needs cleaning, I'd go the dry cleaning route. good luck.