If you want to track miles for gear and maintenance, then that is more the realm of site or software you use to view your ride data that the cyclometer/gps provides. Despite the fact we think of them as sophisticated devices, they really pale in computing power and resources when compared to your PC, Mac or even your own smartphone.
Trying to have everything done by the device is probably asking for disaster, more cost and more complication using them than most of us want.