How often do you have a "Duvet Day"?

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So how often do you take a day off from work....to do nothing? Do you ever ring in sick when in fact all you want is a day under the duvet? I did this only occasionally until I had my son 7 months ago. Now, for obvious reasons I don't get the chance, there are no "duvet days" as a parent. I look back on those days when I could spend the whole day in bed with nostalgia and wish I could do it the odd time again. I suppose when he goes to school...