It is inevitable, they only have so many cycles in them. The best suggestion with modern batteries is to just don't use them unless you need them. That is don't cycle them gratuitously, you don't need to drain them down every so after to prevent memory effects like in the old days.
You can look at the battery stats in your hardware profiler if you want to see about how your battery is doing. Mine says
Battery Information:
Battery Installed: Yes
First low level warning: No
Full Charge Capacity (mAh): 3803
Remaining Capacity (mAh): 3754
Amperage (mA): 0
Voltage (mV): 12484
Cycle Count: 450
That last line also shows my philosophy in this mater after a year and a half of use, use it however you want to and is convenient. Since you cannot "ruin" a battery like in the old days the $100 it will cost me to replace this one when it gives out is well worth the convenience of not caring.
-Eric