How much longer will Zirc or Ceramic last compared to Aluminum Oxide?

Zirc & Ceramic are both considered High Performance grains.  Both will last several times longer than aluminum oxide (3-5 times longer is quite common, while some customers have reported as much as 15 times the life).  Longer life however, is only part of the advantage.  These premium grains will “self-sharpen” during use, which allows them to continue cutting effectively until the grain is worn out. Ceramic grains are the newest technology; their micro grain structure allows for smaller pieces to break away during the grinding process which makes them last longer than Zirc. Aluminum oxide on the other hand gets dull as it wears; the stock removal rate drops dramatically as the grains dull.  As they continue to dull, more pressure is required to continue removing material, which leads to excessive heat & operator fatigue.