Holy Crow that’s some deep bedding and hard to clean. I will say it looks really soft and pretty, not like the wheat straw we bedded with on the farm, when I was growing up(in the U.S.)
Literal straw over here is generally used for birthing stalls, but pine shavings are also used. When I was young, growing up on the farm, we used straw because we raised a crop of wheat, making the straw readily available.
In the last 40 or so years, I think the bulk of U.S. horse owners use pine shavings for bedding. Everybody does, however, bed different - mostly predicated upon finances.
My stalls have had 12”-16” of limestone crush put in them. Mats on top of the crush, then kiln dried pine shavings on top of the mats. I prefer to let the sides of the stalls “bank up”, leaving those shavings build up to help reduce chances of the horse casting itself.
I try keep 4”-6” of shavings in the central/walkable part of the stalls, which are 12’ x 14’. I especially don’t want the shavings any deeper for my foundered horse because he also has a fractured sacrum and deep shavings will cause him to struggle too much to get up when he lies down. He is 15.3H, the other horse is 16.1H. My Arab was only 13.3H and I never bedded him deeper than 4”.
I clean my own stalls. Manure is cleaned daily, urine spots are cleaned every 3-4 days, which isn’t exactly ideal but my horses are on pasture 12 hours so not as bad as it sounds. Old age and money are the two big factors for not cleaning pee spots more frequently but my geldings are amazingly neat and pee in the same areas of their stalls.
Regarding your BO never running out of straw in 12 years— my English grandmother’s favorite phrase was “there’s a first time for everything”, so don’t count on the last 12 years being the marker for the coming years. Especially with the whackadoodle weather the world has recently seen and also the increase in prices on everything under the sun, since Covid came to visit