After lots of charge/discharge cycles, your laptop battery may or may not be at its peak, and sometimes the computer reads the battery wrong. The solution is to calibrate the battery every so often. This fully charges the battery, discharges it to zero, then recharges it again. This is supposed to give it the baseline it needs to make sure that the batteries are being read properly. Typically, at the end, numbers seem to go up (capacity/time), and you can trust your low-battery level indicator. Sometimes, however, it's best not to know!
As you can see in my (low quality) image above, my Max. Capacity for my primary battery actually went down! The secondary battery went up slightly which is what I'm more accustomed to. Since Li-Ion batteries aren't supposed to have the "memory effect," the constant plugged in/unplugged changes aren't supposed to harm capacity. Maybe they're just getting old though. I guess two years is ancient in terms of technology. Sigh. I think that this time I'll repack my own using individual Li-Ion cells from All-Battery. I've had good luck with them in the past and their staff are very knowledgeable (just a satisfied customer!). I wonder if high-capacity capacitors will ever take off and if that will help the portable power situation at all. Time will tell!