IO I assume you are only talking IFR? Most VFR pilots I know update one a year or once every two years. PFMS (the system I use on my EFIS) is updated every 2 hours and updates are free with a yearly subscription so you can update as often as you like. You can update up to 4 devices (in practice) from one account. The file is tied to the serial number of the device.
Rod1