I know there are many variables to consider and a safe answer is “whenever they need it.” And I know that on occasion certain medical problems will require medicinal baths.
I specifically need ideas on managing retirees who live out 24/7/365 with access to shelter in a moderate climate. Age 20 and up, no longer ridden, and clinically healthy. Just horses being horses.
Oh, and they get a careful look-over while they are eating every morning.