Don't drop them, don't hammer them, don't throw them, don't use them as prying tools, don't whack them against any hard surface, and don't subject them to intense Gamma radiation.
These tool tips are made from a very hard material, and as a result they are somewhat brittle. Under normal use they will last for a very long time, but if they are mistreated or abused they may break or chip. For example, if they are dropped on a concrete floor, they may not survive intact. If subjected to intense Gamma radiation, they may become dangerously radioactive and will be hazardous to your health outside of the proper facilities.
Don't use them on really hard materials like files and drill bits.
While they are hard enough to effectively cut most metals, doing this will cause them to wear more quickly and possibly lose their edge. Even though Gary uses one to sharpen his pocket knife, he doesn't recommend this.
The suggested materials to use these on include cast resin, epoxy putty, pewter or other soft metal castings, injection molded plastics, and most other materials that are softer than mild steel.
Don't attempt to regrind them.
Again, these are made of carbide and are very hard. Proper grinding of this material requires a diamond impregnated wheel and a high speed grinder, as well as a knowledge of proper industrial cutter grinding and the use of dust evacuation systems.
If you are not extremely familiar with this sort of thing, just leave well enough alone.
Don't sand them
Many of the abrasive materials used in sandpaper and emery cloth are much harder than this grade of carbide, and if you sand them or use sand paper to remove sculpting materials from them you may sand off the sharp edge.
To remove foreign material from them, use a knife. (carefully)
Modeled and rendered from original prototype drawings and parts, not an actual photograph but an accurate representation.