If it charges properly, I wouldn't worry too much about it. You can try the MagSafe troubleshooting steps mentioned in the CHARGING section of the following link. This should answer most, if not all, of your battery questions:
just experienced something similar to this not too long ago with mine..sometimes it would charge with no light and give me a "service battery" indication but when i disconnect/reconnect the light comes on..when i reboot after that the "service battery" indicator goes away. i tried switching power supplies and haven't had this issue since..