I came here to say exactly this, the graphs are silly. Your demand for energy is fixed - you have a set # of miles to drive per day, per week, whatever, and that consumes the same amount of energy regardless of how you recharge it. You can recharge the battery with that amount of energy many ways, 1000 cycles of 75-65 puts the same total energy into the batteries as 500 cycles of 75-55 or 200 cycles of 75-25. A battery that went through 1000x 75-65 charge cycles damn well better degrade much less than a battery that went through 1000x 75-25 cycles, but that doesn't really help us out considering we have a fixed amount of energy we need to use to get where we want to go.