I've yet to find the GPS that has a long battery life, and for this simple reason: GPS receivers SUCK power immensely. They aren't designed to run without being plugged in for too long, and in my experience, 1/2 hour to 1 hour is about normal battery life.

As an example, I run a routing app for work on a tablet, and without the app running the tablet gets about 10-12 hours of battery life. With the app running (which uses GPS or pseudo GPS) I'm lucky to make 2 hours.

Neil, LiPo are very much NOT like Lead Acid, and "topping up" has lead my family to replacing their cell phones due to batteries that no longer hold a usable charge right around the 2 year mark, while I'm now on year 4 with the same phone, same battery, and I get a week of standby time. (basic flip phone) Though I will probably agree about not leaving them flat for any length of time.