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A lot of owners reserve one trip computer for "lifetime" (and label it as such) and never reset that (so it will match your odometer).
Then choose that to be what you want displayed on the main screen.
I forget how Model 3 works, but I think you can choose "Odometer" as the "trip" computer to display on main screen.
On my X I can choose 3 out of 4 trip computers (one being the Odometer) be displayed and leave the Odometer off, because I have a lifetime trip computer that is in sync with it.
This area automatically updates to display information such as incoming calls, seat belt reminders, current state of the wipers, etc. It also provides easy access to the rear view camera (see Rear View Camera on page 73), charging status (see Charging Instructions on page 156), voice commands (see Using Voice Commands on page 140), wiper controls (see Wipers on page 60), and seat belt reminders (see Seat Belt Reminders on page 29). Swipe to the right or left to access: ◦ Trips. You can display distance driven, energy usage and energy efficiency starting at any time, or since Model 3 was last charged. You can also display this information for up to two trips. Touch ... in the top right corner of a trip to rename or reset a trip.
Yes, B: Lifetime (from delivery day) and I panic to not accidentally reset every time I open it and A: Week and reset it every Monday morning and take a pic of both cards.
Wish there was a way to Lock it or BETTER yet Tesla should add a lifetime card.