I leave mine running when I'm not doing anything. However, I don't leave apps running without it at least plugged in. Especially anything that uses hardware such as the GPS or leaves the screen on. The NITS are designed to run for up to 10 days on standby with the screen off, so if you're running short on power, it's likely from the wifi, since you had gmail notifier and all those other web apps on, which would have at the very least ate your battery from being on.

My suggestion is that if you're gonna have all those on, you need to set them to either only run when the wifi is on, or set the wifi to auto timeout after 5-10 minutes. When I'm traveling, the wifi is on for as little time as possible. If an app needs the internet for something, then tough beens. It has to wait until I connect again.

On a side note, as for the stuff in your sig about "want to get" for the case, get the HP Jornada case from Overstock. It's just $5 and it fits the nit like a glove.