Yeah my laptop has a 'power saver', 'balanced', and 'high performance' mode that you can set when on battery power.
Power saver is like an 8 hour battery life where the high performance is like 2. Of course, I never use the battery so I stay plugged in and tend to ruin my batteries this way (although I often knock the cord out or something so it's nice to not have it die on me).
In addition, I keep the battery mode on 'power saver' so that when I do knock the power cord out, I realize it immediatly.