The manual recommends a recharge daily. This is because Li-Ion battery last longer if the battery is not drained dry before a recharge. Palm V alerts you if your battery is running low. If it gets any lower, it shuts off. I'm not risking a flat battery and had never done so.
Information is from the manual.
This prevents complete lost of start-up program if you ever completely drained you Palm. I downloaded the Palm OS 3.3 update from the web while waiting for it to charge. The unique feature of Palm is that it allows new programs to be installed onto the device. Latest OS now is version 3.5.2. However, it is not for free.