How many horses should I expect to get out of each blade / rasp?

This depends greatly upon the way in which the blades are used.

The economy of blades can be somewhat enhanced by rotating each blade in other float handles for attending to other teeth in the dental arcade. Whilst it is advisable to use sharp, efficient (new) blades on the major portion of all molar arcades, a slightly used (or ‘conditioned’) rasp may be preferable when shaping the foremost side facets of the first upper and lower cheek teeth. The lifespan of rasps can be greatly enhanced by rotating them between the various float handles used to float the teeth, rather than exhaust each blade in only one particular float handle.

Initially, a brand new rasp is best suited for floating the bulk of the molar arcades, as the blade itself is drawn along the line of the teeth, and is less likely to grab. It's also beneficial for the practitioner, as a new blade makes light work of this rather substantial part of the overall job. Once the rasp begins to lose its ‘bite’ on the molar arcades, it still has plenty of life left in it for floating the foremost premolars. The float handle used for these purposes often has the blade housing offset at an angle, which means that the pressure being applied to the tooth is also directed from an angle.

It's suggested to first transfer the used (or ‘conditioned’) blade to the handle used to float the 2nd, 3rd and sometimes 4th premolars (or 1st, 2nd and 3rd cheek teeth). The slight angle of the blade housing tends to put the ‘bite’ back into the blade due to the angle of the pressure being applied. Again, as the rasp will eventually begin to lose its bite on these particular teeth, it's then suggested to transfer it to the float handle used to shape-up or contour a bit-seat on the front portion of the 2nd premolar. As this handle commonly has the blade housing angled more abruptly, the rasp will again regain much of its bite as the pressure is being applied at a greater angle.

Please note that a well-conditioned blade can also be transferred to the handle specifically designed for treating the last upper molar (6th cheek teeth). This molar, when sharp, is often the cause of lacerations to the cheek tissue, which can sometimes make the horse sensitive to the floating of this tooth. A well-used blade can sometimes be beneficial here, as it can be used in a gentle ‘sanding’ motion (that is, short forwards and backwards movements) which many horses seem to tolerate much better. Being a well-used blade, the equal pressure being applied in the ‘wrong’ direction will not impact heavily on the lifespan of the blade as would be the case on a relatively newer rasp.

Of course, no one should lock into rotating their rasps in the exact manner described above. Based on personal techniques and preferences, a practitioner may find it more beneficial to adapt to their own rotation system.