It’s Not How Sharp The Teeth Are, It Is The Horse’s Threshold Of Pain
The frequency of floating a horse is variable and is related to the individual horse. Often, we think of prevention on a mechanical device, like how often do you change oil in a car’s engine.
A horse is a living thing and not a machine. It is the threshold of pain that determines how frequently you need to float. In other words, how they perceive the sharp points against their cheeks and tongue.
Other determinants are genetics, age, and discipline. Some horse’s teeth are softer or decay more easily. Older horses have harder enamel and erupt less. Certain disciplines require more bit contact while others don’t require a bit.
The least determinant of frequency of floating should be the cost. Because the benefit of preventing pain inside the horse’s mouth is well worth the little annual cost you spend getting it done. Plus, this one preventive act may help decrease other costs such as lost hay and grain (spilled or not eaten due to pain), lost training time (horse is more compliant and willing to learn), and decreased vet bills (a more comfortable horse is usually more healthy).