I don’t know the best recipe either, but from what I know the middle charge states are indeed the best for lithium batteries. I have also heard advice that it can be useful to do a deep cycle with letting the battery run down and then charge it all the way up every so often (not more often than monthly), but not sure what’s in that. Allegedly that helps to reset the controller so it knows the maximum charge or so.
These links might explain things much better:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
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