I board my horses. One has a stall, the other prefers to live outside unless its really really cold. We're in Wisconsin, at a show barn with 30 some horses. The stalls get mucked daily to get manure and wet shavings out of the stalls. Shavings are added as needed.
I think they get stripped once a week, lime is used when needed in the winter since the barn doors are closed most of the time. We're big on stall mats, so that cuts down on any build up of urine spots and smells. It's easier to get the stalls cleaned with mats under the shavings.
Luckily most of the horses still go out all day unless the turnouts/pastures get too icy, so they get lots of fresh air and the barn air gets moved around.