Don't charge it to 100%.
Try and get a software suite that keeps it charged between 30% to 70%.
Lithium Ion cells are good for what they are, but they are quite possibly the most volatile type of cell used in consumer items. The membranes inside the cell on the annode corrodes regardless of its charge state, however, having it fully charged accelerates this. Having it fully discharged is equally as harmful. In addition, the rate of ware is also temperature dependant - and as we all know, laptops can get quite toasty.
So, if you want to prolong the life of your cell to it's maximum and usually sit with your laptop on charge, charge the battery to about 70%, take it out, put it in a air tight container and plonk it in the fridge. It'll then last far far longer. Of course, that's hardly practical if your on the move a lot.
I'm pretty sure IBM have a software tool that allows you to pre-set the maximum to charge the battery to. I had it in an old X40. It will likely work with any other laptop I'd imagine. Set it to a max of 70% and perhaps automatic shut down at 20%. You'll only get ~50% of the usage out of it per charge (actually, due to the tollerances in the battery monitoring software causing non-linearity, you'd perhaps get more
), but it'll prolong the life of the battery to about that of the laptop itself.
Car manufacturers use this technique to prolong the life of the battery packs in electric and hybride vehicles - where the long term cost of battery replacements would prohibit the total cost of ownership, of said electric vehicles, from being competitive.
There ya go, an answer, a bit of an explination, and a suggestion.
Hope that helps.