The rate at which a hoof grows and wears depends on several things, including climate, terrain, genetics, nutrition, and daily use, to name a few. Your vet and farrier should be able to tell you how healthy your horse's hoof quality is. A healthy hoof has a characteristic odor. Once you learn that smell you know immediately if an unhealthy hoof is being trimmed.
If the hoof quality is good, don't worry too much about the growth rate. Most research shows that some horses need trimming every six weeks, while others are fine with up to 12 weeks, depending on the individual horse and the work and performance the owner expects from the horse. Humans, too, can get an extra month out of a favorite pair of worn-out work boots, but that last month might not be good for our feet, and the boots might not help under adverse conditions.
We see lots of horses coming through our shop with long toes that are stressing tendons and ankle joints, due to farriers who are rarely aggressive enough to knock the toe back, along with owners who don't know the importance of regular trims. No part of the hoof, especially at the toe, should have a ski-slope look.
Improper angles cause stress on growing joints and negatively affect a working joint's ability to remove toxins and lubricate itself. These situations often set the stage for the early onset of ringbone and other arthritic conditions in pre-teen horses.
Many times a toe is too long to set back properly with just one trim. If a toe is excessively long we trim it back every few weeks. The shorter interval between trims helps the white line migrate back to its proper position. Long toes also contribute to under-run heels. Keeping the toe short helps build a strong heel and, in turn, gives much better tendon support.
If your horse requires regular trims that are hard for your farrier's schedule to accommodate, learn to rasp off the edges. Rasping takes a bit of strength and finesse, but many owners can learn to do it. Also ask your vet and farrier about the hoof's health. A simple change in diet or other environmental factor may help keep the chipping under control.