I decided to follow the lead of my car's built-in trip computer and refresh the values once every 1000ms, or more accurately, to refresh 10 values per second, one at a time at 100ms, 200ms, 300ms, etc.
I also prioritised things that change more often, like instant consumption, RPM and a few specialised sensors. Things like battery voltage, temperature and fuel levels only need to realistically be polled every 5, 10 and 20 seconds respectively, so there's lots of room for prioritisation.