All iPOD batteries have a FINITE amount of charge/discharge cycles in them.
If you only run down the battery a quarter of the way every day, then you are basically putting a quarter charge back on each time. Four days of this would equal one FULL discharge and recharge cycle.
The only time it really matters is when you first get the iPOD and need to calibrate the battery meter. To do this, you charge the iPOD up to full, and then put it into play mode and let it play and play until it is totally out of juice. The easiest way to do this is to put it into shuffle and repeat mode and just let it go without listening to it. Turning on the backlight the whole time will speed the discharge process.
You will get a little warning message telling you to plug it into the wall when it is done. Charge it back to full and the calibration is complete.
You shouldn't need to do that again unless your meter starts giving you a false reading.