My husband also sleeps quite a lot during the day - sometimes a deep sleep. At first I thought I should be intervening and waking him as I thought it might be the wrong sort of routine for him. But, he does sleep through the night as well so I decided that I'd take advantage of his day time sleep to have time to myself. If his night time sleep was being affected then I'd probably think differently about it. I'm not sure if I'm doing the right thing but as he seems to be exhausted all the time, it seems the kindest thing to do. If you are concerned perhaps it might be worth having a word with your GP about it.