I've done a lot of research on Li-ions with the internet battery gurus and there's some very simple charging practices that you can employ to get it to last significantly longer if you want, depending on what your average daily usage is. First to clarify some myths..
It is true that you will not overcharge (or overdischarge) a Li-ion. To charge above 4.2V, or for that matter discharge below some number, I think 2.7V, starts to destabilize the battery chemistry and creates a serious potential for explosion or flame venting. As you can imagine, manufacture's will avoid this at all costs and so smart circuits exist to prevent this from happening.
There really is no need to fully cycle a Li-ion as it has no memory effect as previous battery chemistries. However, manufacturers recommend doing this periodically because you are constantly losing some capacity (the battery is wearing) from day 1, and the internal battery meter needs to be "reset" for this. Nobody like it when their device shuts down with 20% remaining on the meter.
From the evidence I've seen, after high temperatures, the second highest stress factor for a Li-ion is high voltage (or 100%/4.2V charge). The greater the % of time the battery reaches and sits at this level, the faster the battery will capacity will be lost. Of course the battery is designed to handle this, and the manufactures' charge cycle quotes account for this, but the point is, if you terminate charging at 90%/4.1V instead, you can double the number of charge cycles, not to mention that you will retain a higher capacity for longer into the batteries' life.
So for simple good charging habits, I merely use a light timer set to terminate charging at 80-90% (based on my best guess) and just before I wake up and start using the device so as to minimize the time it sits at relatively high voltage. It only adds a few seconds a night to the charging routine and should preserve the battery well into years 4-6 when it will be in the hands of my kids, if nothing else, as toy.
This is good for further reading...
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
Having said all that, spending a few extra seconds at night, or leaving the house with 10-20% less capacity, is often considered too much for a device that will likely be obsolete and replaced in a couple of years anyways.... I don't disagree, but I tend to use my stuff way longer than the average consumer.
