DTH bit is the tool cutting rocks, and subject to severe stress from the striking piston as well as from the abrasive cuttings passing the bit at high velocity. When selecting the right bit for optimum performance you have to balance penetration against bit life. On occasion you can successfully sacrifice bit life for penetration. In such cases remember the rule of thumb that states that a 10% increase in penetration covers at least a 20% loss in bit life.