Currently running 4 M42+ knives on my jointer cutterhead, which i think are the predecessor to the currently offered M+ knives. Honestly, i have no idea of how old these knives are. In any case, im thinking about switching out for carbide knives instead of repeatedly going through HSS knives every 6 months. From anyone that has carbide Tersas, about how long can i expect them to last? I process about 2,000 bdft of rough lumber a year. Nowhere near pro shop, but more than the typical weekend warrior. The knives arent cheap, but im thinking i can get two carbide knives and run two HSS knives to balance the head. This would cost me about $250. Not sure if i gain much performance by going to 4 carbide blades. The purchase makes sense if these knives will last as long as the byrd inserts in my planer. Im pretty sure i can go 2-3 years without rotating. I rotated them once after 1.5-2 years of use thinking i had grown used to dull cutters, and i didnt notice a surface or performance difference. Lastly, it looks like Rangate offers some form of diamond coating that they allege to last longer than carbide. Does anyone have experience with this coating?