I used the service manual procedure with mine being a year past due and it reset. (schedule b with clock) So I don't think there is a non resettable threashold.
I held step 4 until it beeps, then release. Make sure you turn the key all the way to the 'on' position and not just 'acc' position (dash will light up like Christmas tree/ fans will run in full on) One thread poster reported getting '-49000' displayed with reset on 'acc'.

"Perform the following to reset the counter:
1. Turn the ignition key to the ON/RUN position.
2. Within one second press the ****/button to the left of the display twice.
3. The present status for days remaining or distance traveled is displayed. Within ten seconds turn the key to
OFF.
4. Press and hold the ****/button to the left of the display, while turning the key to ON/RUN again. The present
status for days remaining or distance traveled is displayed once more. Continue to hold the ****/button to the left
of the display.
5. Release the ****/button to the left of the display. After approximately ten seconds, a tone sounds and the
display shows 7,000 miles (11,000 km) for approximately ten seconds."