Never. I couldn't do it and wouldn't want to. Shower, hair, make-up, and perfume every morning without fail. Being dressed and groomed doesn't stop you putting your feet up if that's what you want to do.
Doesn't feel right to amble about in tracksuit bottoms and slippers. Sleep as nature intended, if nature wanted no clothes. Feel more responsive if fully dressed. Hate lying in bed too long.
I used to know a woman who never left her bedroom before she had done her hair and put full make-up on, despite having a couple of boys. When they were going on holiday, once her husband and the children were in the car to go, she returned to the house and dusted and vacuumed all through.
I have never had a duvet day and most likely never will. When I open my eyes in the morning I immediately get out of bed and I am out the door with the hounds within 5 minutes. I wash and do breakfast, drink coffee etc when I return. I don't possess pyjamas or a dressing gown, I have never had the need for them as an adult.
Why would you feel guilty about wearing comfy clothes? That's all PJ's are...comfy clothes. My OH put's PJ's on after his bath/shower and takes them off to go to bed.