The advertised life of the 405 is much longer than what she is getting, 8 hours in training mode (according to the Garmin web site). She can run the 405 with the HRM and cadence unit and get close to the advertised hours out of a charge. It drops dramatically when she turns on the GPS option in order to collect the data. I am assuming that the 500 works in a similar manner. If it provides up to 8 hours of battery life on a single charge it would be a consideration, again, since century rides can last that long.

The really nice thing that I like about the Garmin is that you can set it up to see more than just 2 or 3 readings on how you are doing. Currently, with my Cateye Double Wireless, I have to flip from mode to mode to see what my cadence, total miles and ride times are. It would be nice to be able to see all of it on the same screen.