Somewhere I read that about 3 hours a day is typical for a hrose to lay down. It's just that we don't always see it, as it may happen part in the middle of the night, and part in the late afternoon (( 3to 5 is often a time of low circadian rythms for horses, meaning they are logey)
Some horses do fold up tighter than others while laying down and their shod hoof can cause a callus on their own elbow. There are these donut like things a person can put on to disallow that .
Bathing is never required. Bathing with soap is not a great idea, as it takes away the natural lanolin/oils of the skin. Having some dust against the skin helps keep the mites down. However, grooming also stimulates the skin, so it can be good, too. I only wash off the sweat on occasions. The horses never seem bothered by it. I towel off as much as I can. But where we are, there is no heated water or warming lights , so kind of primitive. And the horses are very happy and healthy.