What a nice question.
I give my horses twice a year a view weeks of. And they love it. They get more happy out of it with a new fresh and clean mind.
The first time is during our holiday and i give them some extra more weeks off, before and after our holiday. And in december they get free time. Most of the time i am very bussy then all things must be ready before the end of the year X-mas days and so on.
For me are those times that i live with an "agenda" and that is not working for my horses. They will walk away or dont wanna do anything at all. So i had decided to give them time of. Last year (2009) they had a extreem long time off, from november till march.
I think they love it. In the months they get their wooly coat i do less intensive work but keep them on a light base at work.
What you wrote about iceland is true for some horses i think, it depents on what kind of work they have to do.
The horses who used during the summer season for ridingholidays by tourists get the winter time off. And they will need it
It hard work for them. I know it i have seen them many times.
I do not like such big trips with lots of people some can ride and some not. (only pulling reins) I have ridden their too but only me and my husband and the woman who run the farm outthere. We have visit them several times.
Almost bought a horse too
They get the winter of because there is not enough money to earn from visitors and there is too much snow to make long trips. So it is not only for the health of the horse but also a supply and demand.
The horses who are used for competition are working during the winter time. They get stabled and have to work. As soon the spring is comming they go back in the mountain fields the get their rest. They go in big groups with lots of youngsters.
It is so beautyfull to see those horses in long lines along the hills. Trotting and tolt next to eachother.
The horses who have reached a certain age get trained in the early spring for a 3 months and they get rest after that period. And in The winter they get some schooling again. Then if they are lucky a new long holiday and then they have to go for the real work.
So yes people out there have a bit more dependent on the seasonal times then we have to do.
The difference i see with my ponys, when they get time off, they are very close to eachother. The day's exist of eating and sleeping and sometimes depents on the weather of that day some play time. During the first snowfall they are very playfull.
The day after when everthing is white, they only wanna eat and sleep
They will only food from me, no play interactions or what ever, just food...food....food....
i am not worry about that, it is there special time off. Get their minds free of our human interactions and must do's and dont's. Or what every we wanted from horses. When the time is ready for work again, they are pleased to go out again and explore the new world. With fresh new green leaves and flowers .
I can't hardly wait for it