The lithium ion batteries wear portable due to two factors: 1) the active use of the laptop battery and 2) the natural aging of the laptop battery. Both the notebook's battery wears out over time, the trick is to minimize its impact, while still getting the performance of your laptop battery you need.
The most important thing to understand about laptop batteries is that they are always losing a small piece of his office. The hotter the temperature, the faster notebook batteries loose their charge. So rule number one is: keep calm laptop battery. Notebook battery manufacturers store their products in around 60F. (It is no use to them dell laptop battery in the refrigerator, and you may damage the battery by freezing.)
The second most important thing to understand about laptop batteries is that their capacity is reduced with each cycle of loading and unloading (or employment). By itself, this is not surprising - but when combined with the previous point leads to a startling conclusion.
When laptop users leave their laptop battery inside the machine, but leave the computer connected to the wall, the laptop battery is in a constant cycle of loading and unloading. The notebook battery is sitting unused in the notebook, discharging a little faster than normal due to the heat of the laptop. Once its charge level drops to a predetermined level (which is different for each manufacturer), the AC adapter provides extra energy to "finish off" the laptop battery. As the laptop battery gets older, it tends to self-discharge a little faster, which further accelerates the process.
The lithium ion batteries normally offer portable 600-800 charge / discharge levels of 1.5 to 3 years of life. When using the laptop battery as described above, are unnecessarily using their skypemate power to recharge.
One additional note: many older people remember that the laptop batteries on early computers worked best when they were fully discharged before recharging. While it remains true for the technology of nickel-cadmium batteries Lithium Ion laptop today work best when they are recharged when they still have 10 to 20% of remaining capacity. So if you are using the laptop battery on a long flight, try not to fall into the habit of using the notebook battery until it has almost no cost. The battery in your laptop, literally, not be the same when you reload the next time.