My friend who had a pair always said they were about 98% couch potato, but every so often loved to go out in their (smallish fenced) backyard and tear it up in tight circles as fast as they could corner for what seemed like forever.
I'm not a vet, but in humans, over sleeping or extended periods of sleeping is usually a sign of depression.
yes, in HUMANS. i would encourage you to do some research on greyhounds before making all kinds of erroneous assertions about them. they are frequently referred to as "45 mph couch potatoes" for a reason. they do not need a lot of exercise. as you stated, you are NOT a vet.
Murray, most if not all that we see in public are rescues. The tail tucking is a common stance for this hound, however when really really excited and happy they can clear a coffee table with one swipe. No tall candles at tail level for these guys. Just had a thought...has anyone ever seen a greyhound advertised for sale or at a shelter? I have only seen them taken in by the numerous rescue groups who are so very dedicated to this breed and determined to find them a good home.