Erm, is it a NiCad? if not, keeping the cycles down is the best route to economy. They count them if I'm not mistaken!
Deep cycling NiCads was vital, but I think it was the last one that required that. I'd be interested to know if there are others.
The Sony ones are LI-Ion. I try to keep them at 80% with some swings just to blow the cobwebs out.
I have had a knock-down drag-out with Sony over theirs. They discharge up to 15% a day with the computer off. An I mean OFF.
What's worse...for 9 months, none of their helpline knew.
When you're traveling and can't always get to a plug, that discharge can be tedious. They've given me another battery, but I still find it best to undo the thing for making sure I've got power when I need it, but then I have to make sure it's safe for travel. i.e. no metal bits that could short it.