I found some time in between trips to play around with different combinations of time and distance for the service reset.
For the 2018 R1200 GS TFT it seems the maximum time is 3 years for the current date and the distance is 60,000 km from the current odometer reading, any thing exceeding these will set to these maximums. Interestingly the dash updates immediately without having to cycle the ignition and the app also shows the new settings right away (which I think it already did).
Some people might wonder why you would want these extremes but I don't think I am alone in finding the service reminder useless and a pain in the butt, a oil life percent would be more useful (which is common in 4 wheel applications).
Well time to finish cleaning up from a dusty Dualsport trip and prepare for more dirtbiking before leaving in September for a month in S.A. (the home of Hex Code, (hope the service reminder doesn't go off on the rentals
)