I never use a laptop without AC power. That wouldn't damage the laptop over time, would it? Because I've had this HP dv6000 for two and a half years. When I actually do use the battery, maybe a few times a year

o) I only get thirty minutes of life. Granted, it only came with an hour or two of normal battery use. I have never calibrated it either.
It won't damage your laptop, but as you've seen, it reduced the capacity of your battery faster. You'd be wise to use it once or twice a month (at least one "cycle" per month, i.e., one full recharge--but you don't have to do it all at once and can do it as, say, two times of using the battery down to 50%, then recharging, etc.). It's also good to avoid excessive heat--so, for example (unless you live in a cold area), don't leave it in your car during the day, especially in the summer.
Lithium-ion (and probably lithium-ion polymer, like in the MacBook) batteries permanently lose capacity over time, but in addition to time, which you can't control, factors you
can control include temperature, frequency of use/cycling (already explained), and the capacity at which the battery is "stored." They permanently loose less capcity when around a 40%-60% charge and stored close to 32 °F (some studies say as little as 2% loss per year) compared to 100% charge at room temperature (which may lose as much as 20% per year, maybe more due to higher temperatures such as those created near the laptop by the laptop itself). Unfortunately, refrigerating a battery is inconvenient, and most (all?) laptops don't really let you keep the battery installed but maintain a 40%-60%, rather than 100%, charge. Thus, while good to do, this may be difficult or inconvenient.
But back to your battery, bascially, next time, you may want to use the battery a bit more frequently (at least once a month) and, if you're not going to use it for an extended period of time, store it charged to around half- rather than full-capacity, and, if you feel so inclined, maybe even pop it in the fridge (although I was always nevous about moisture when I did that)...if you care about your battery that much. I guess if you never use it anyway, it might not matter.
