Some of my patterns have some extremely long cuts in them. That will throw off the average cuts per blade. I tend to believe that heat is the major cause of blades losing their set and temper. As mentioned previously, the hardness of material, thickness including layer cutting, and speed all have something to do with blade life. But buying blades by the gross brings the cost way down and so I don't even worry about this anymore. When I can no longer feather the cuts, smoothing out the beginning to the end of the cut, I chuck it and put in a new one.
This Yin Yang Tree cut in a two stack of 1/8" Baltic Birch, was one long cut, so to not heat up the blade I ran a slower speed and took it slow on all the tight turns.