The Least Useful Guide to Fukuoka

To reduce frequency of washing duvet covers this winter (as I am too busy washing clothing after every outing to take care of bedding items), I covered the top of duvet cover with a face towel and safety pins, which looked a bit scary (to my husband) but worked. 

My husband firmly rejected this idea because of the possibility to get pricked while sleeping (If so, I think the safety pins would not be dubbed "safety" in the first place).

So, I have introduced store-bought duvet-top covers (around 1500 yen each at a local futon store).

It is bigger and more likely to stay in place and easier to wash compared to duvet covers. It still need a couple of safety pins just in case, but my husband accepts this.

Then, how often am I supposed to wash this thing? And how about the duvet cover? I wonder if there are nationwide or worldwide statistics on how often they are washed.