Rather than address this on your point by point presentation
Depth of Charge refers to the amount of charge necessary to bring the battery
Back up to a fully charged state. So… if you start charging it at 30% full, the Depth of Charge for that cycle would be larger than if you start charging it at 80% full.
Now, the two concepts work together like this. You get the most number of Charge Cycles when you only charge at an optimal Depth of Charge every time. One of the thing that reduces LI-ON battery life, are micro charge cycles… namely keeping the battery in the unit while using it, and rarely using it on the battery at all. The battery will discharge normally, and using it in this manner will cause the battery to go through several micro charge cycles in a single usage session.
So… what is the optimal DoC to shoot for ?
Now… I’m fully aware of the fact that you can’t remove your battery.
This means you have two choices. Either always use it on battery, and only charge it when the DoC is optimal… or deal with the micro charge cycles and see your battery capacity drop to half in about three years. Unfortunately, since you won’t be able to use the unit on just the AC power (like you could with a laptop), you will be forced to be charging and discharging the battery all the time. Which means that even if you always religiously used it on battery, and didn’t charge it until it hit 40% every time… you’d still see your 6.5 hours throttling everything drop to about 4 hours after three years… possibly just after two.
And let’s be clear… that 6.5 hours is with the screen dimmed to the lowest it can be, and allowing the processor to idle as much as possible, as opposed to doing work which makes the processor run full out all the time.