Newer batteries work better. To obtain the longest life from your batteries, don't fall for the myth that says you should fully drain the battery before recharging it. In reality, a battery has "X" number of hours of use in it. If you're using some of those hours to simply drain the battery, it won't last as long over its lifetime. Just use the battery normally, and charge it when the battery needs a charge or when you're done shooting. A partial charge isn't going to significantly affect the life of the modern battery. That may have been the case with rechargeable batteries from several years ago, but it's not true with newer batteries.