I just realize you can repair horse saddle with cobbler kit. I don’t think you were able to do this before (maybe fixed in a patch).
It seems like the horse saddle losses condition very fast so I am not even sure if it is worth it to keep the upkeep of a saddle. Does a 100% condition horse saddle just provide better combat protection and reduced conspicuousness?
Nope. No difference.
Only if your horse is attacked then it will deteriorate.
I have gone for long periods at 100% until I was attacked while horseback or some idiot attacked Roach.