A traditionally shod hind foot - note how much more length is in front of the widest part of the foot than behind it
These shoes were also only on for two or three weeks before they were worn out and needed to be replaced. Indeed, in the 1950 British Horse Society Manual of Horsemanship it states that if your shoes aren't worn out in three weeks, book an appointment with your farrier so that he may remove the surplus foot growth to keep your horses limbs in balance.
Many years ago I used to shoe hunters at Melton Mowbray. These horses did twenty miles of roadwork a day, getting them fit for purpose and every extra day we could go before shoeing was considered a bonus, three weeks being the maximum we could achieve. Working horses in this was gave rise to the misconception that shoes should only replaced when they are worn out. If horses are in hard work this is the case, but as it is through the toe that power generated in the muscles is transmitted into forward movement, it therefore follows that it is the toe that is meant to wear and by putting shoes around the toe we prevent this from happening. If hoof balance is not maintained and the shoes are left on too long the toes elongate and a slow slide into lameness starts.
Today's horses do very little work on abrasive surfaces or in straight lines. They generally work on a soft surface in a school and in circles which means the backs of the shoes are fitted short and tight to reduce the probability of lost shoes. When support is removed from the back of the hoof, nature compensates by increasing horn production in the front of the foot to try to maintain the pedal bone in it's correct position, causing the toe to elongate faster and reducing still further the function and ability to absorb concussion. This removal of support from the back of the hoof both reduces the ability for the foot to absorb concussion and prevents the pedal bone from lifting into the position needed for the third phase of the stride.
Unfortunately, with a traditional shoe on the foot, the toe is unable to wear and therefore increases the speed at which the toe becomes long and ultimately the heels will collapse.
These days however there are a number of early break-over shoes which remove leverage from the toe enabling the farrier to give greater support to the back half of the hoof as they are placed around the pedal bone rather than around the toe. This allows any surplus toe to wear provided the heels are lowered to the widest part of the frog. The shoes are fitted bold from the widest part of the hoof back and, most importantly, the wall at the front of the hoof is left in situ, only removing any flares. Removing excessive wall from the toe removes stability causing the hoof to over expand.
The most well known of these early break-over shoes are "Natural Balance" shoes, who also make "Centre Fit" shoes. These are made with the middle of the shoe marked; if the marks are placed at the widest part of the foot break-over will occur just in front of the front edge of the pedal bone. They are also graduated from the centre to the outer rim of the shoe reducing leverage in all directions, helping circular movements on soft surfaces and preventing the joints from reaching the extremes of articulation when turning and reducing repetitive strain injuries which are becoming all the more common in modern horses and are so very hard to diagnose.