That graph is pretty persuasive -- if you do an eyeball average of those curves, the pattern is clear. The less frequently and less deeply that the battery is discharged, the more cycles you will get out of the battery.
So the lesson is to keep it topped off and never use it! ;)
No, seriously. There is a hidden message, I think -- this is a big argument in favor of solar. Instead of running the generator every so often, keep the juice flowing all the time, as much as possible, to extend the life of the battery.
It is even an argument in favor of permanent panels, instead of portable -- my portables only perform when deployed, not while we are on the road or stopped for lunch or whatever. But I still prefer portable solar because it allows me to park in the shade and still get some power, by moving my panel into the sun.
Life is a series of compromises.
