How sleepy can you be?

I have never seen a breed lazier than my two whippets.. It appears to me that they sleep at least 20 out of 24 hours a day. They do get up to eat - trust me, they would never ever skip a meal - and to take a peek outside, but most of the time, they crash on the couch. Or on the deck. The lawn. Their bench. A blanket on the floor. Anything. If only it let's them do what they do best: sleep. What a life..