It's great that your set-up is working successfully. In college I was a mechanical engineering, mathematics, and theoretical physics major. Four months is still premature for an accurate assessment of the battery, and the reason is simple.
A lithium ion battery is what they call a solid state battery. Lithium ion batteries tend to also maintain their integrity longer than lithium polymer batteries. In any arena, an overcharge is never good. Think of your vehicle. Your vehicle battery is rated at a specific cold cranking amp. The larger the engine, the more CCA's in the battery typically. Also, you need to consider the vehicle alternator. Alternators are capable of overcharging leading to degradation of the battery. It is not an overnight process but a period of time where increased voltage eventually ruin the battery.
Obviously Androids don't have alternators (yet) but the job and purpose of an alternator is to maintain and feed proper voltage. Think of your car charger as the alternator. Essentially its function is quite similar to an alternator - both charge the battery. Obviously a multi-cell car battery has different chemistry and physics than a lithium ion battery, but the similarity is both will suffer if amps and volts exceed the recommendation of the manufacturer.
I'm not telling you what to do. It's your equipment and you can do with it what you wish. There are few physics and engineering geeks such as myself, and I certainly wouldn't expect typical, even educated consumers to know that info. But that's the science behind it, and with this information I only wanted to explain the probable outcome of overcharging. I hope I was a help.
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