Interesting. I was quite worried about Joe the other day, as we'd had to sedate him to do some things to him (poor boy) and he kept on lying down. Eventually, OH put his head collar on and dragged / coaxed him up, but the poor thing lay down again 5 minutes later! It doesn't appear to have done him any harm, but I do know that I read somewhere that their internal organs can be damaged by laying down for too long? Joe does like his snoozes - he often settles in for a lay down at lunch time.
During the winter I find them both lying down in the school together - I think the idea is that Storm is meant to keep guard, but sleep gets the better of her and she ends up joining him...........!!!