Power Cycle count number question

Keep your computer plugged in whenever possible to reduce the cycle counts.

“Batteries have a limited amount of charge cycles before they are considered to be consumed. Once consumed, a replacement battery is recommended. You can use your battery after it reaches its maximum cycle count, but you may notice a reduction in your battery life. Knowing how many charge cycles are on your battery and how many are left can help you determine when a battery replacement is required. For optimal performance, replace your battery when you reach the maximum cycle count.”

http://support.apple.com/kb/HT1519

In this article, Apple says DO NOT leave it plugged in all the time:

http://www.apple.com/batteries/notebooks.html

Look under the section, "Standard Maintenance":

For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her notebook on the train, then plugs it in at the office to charge. This keeps the battery juices flowing.

I've worked these forums a long time and I've lost count of the number of posts about premature battery failure that begin: "I don't understand! I never use the battery!"

I try to do a minimum of one cycle per week.

At a certain point it really doesn't matter.

http://en.wikipedia.org/wiki/Lithium-ion_battery

On average, lifetimes consist of 1000 cycles,^[97] although battery performance is rarely specified for more than 500 cycles. This means that batteries of mobile phones, or other hand-held devices in daily use, are not expected to last longer than three years"

So definitely heat, cycles and overall age is a factor. Rarely do you hear even shelf lives of over 4 years.

http://en.wikibooks.org/wiki/Battery_Power/Lithium_Ion_Batteries

"A unique drawback of the Li-ion battery is that its life span is dependent upon aging from time of manufacturing (shelf life) regardless of whether it was charged, and not just on the number of charge/discharge cycles. This drawback is not widely publicized.

At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 degrees Celsius or 77 degrees Fahrenheit, will irreversibly lose approximately 20% capacity per year. However a battery stored inside a poorly ventilated laptop, may be subject to a prolonged exposure to much higher temperatures than 25 °C, which will significantly shorten its life. The capacity loss begins from the time the battery was manufactured, and occurs even when the battery is unused. Different storage temperatures produce different loss results: 6% loss at 0 °C/32 °F, 20% at 25 °C/77 °F, and 35% at 40 °C/104 °F. When stored at 40% charge level, these figures are reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively." (citations needed)

So it's generally accepted to store unused batters at 40% charge at 0º C.

Impossible in a laptop daily usage situation.