I don't know about this unit but one GPS unit indicated that the battery will perform at up to 90% for 300 charges or thereabouts. I.e., after a year of constant use it will need to be replaced or the unit junked. For people on multi year tours, it will be an extra expense to replace the unit or the battery (if that is possible). I have an LG cellphone that works fine but the battery is good only for an hour or less of use, even after replacing with an OEM battery which was good for a few months. The rechargeable battery technology is good only for those folks who keep up with the technology which churns out new models of the same device at least once a year. Someday, the magnetic pulse based cycle computer technology will be completely replaced by GPS technology (like digital photography eclipsed chemical) but it still seems a few years in the making. For the measurement needs, GPS is an overkill over the current cycle computer technology which runs for a year on a single CR2032 battery. For navigation, it may be justified to have a GPS for occasional reference. I have a Garmin nuvi GPS unit (for car) that just died when I was trying to load some waypoint file to see if I can use it. Would not even power up now. Another one now takes forever to locate satellites after I updated the firmware and maps. Someday, GPS units will be as cheap and more importantly as reliable as digital watches and magnet based cycle computers.