The other thing is, battery life degrades over time, which is relevant if you don't want to be buying new devices every couple of years. When I got my Garmin it probably held a charge for 6-7 days. After four years, that is probably closer to 4 days, which is still pretty good. If less than a day is the starting point, I can imagine that after 3+ years the battery life will be poor enough that you regularly end up wearing a paperweight on your wrist for some portion of the day.