Yes Uncle Cooperman it is a very long drive. I had the standard 13H748 idler gear bearings disintegrate on the Alaska Hwy in Yukon on the last ALCAN Summer Rally in 2018 (it's held every 4 years). The rest of the Mini did very well.
That bearings failure was so total only the circlips were still trying to do their job. As a result, a complete teardown and rebuild was needed, with new transmission case & drop gear housing. I sourced German made Schaeffler Group 1212 INAs a direct replacement for the Torrington 1212s used in production. The rebuilt power unit has done very well.
As for the driveshafts, they are the original yoke type shafts used by Leyland Australia in 1973. The rubber u-joints are gone, as are the QH successors, in favour of alloy cupped joints designed by Graham Reid, Heritage Garage, California. These joints are readily greased, no need for grease needle etc. The Mini had 12" wheels and 8.4" Metro 2-pots when I bought it, so it has had the related outer CVs for more than 12 years. Our Stages are TSD, so not flat out as the Rally is more in the style of the early Grand Touring events. That said some days are pushing 1,000 kilometres.
Long story short, I am less concerned about drive shaft failure than ground clearance and tire failure. Mini will have the sump guard in place and the exhaust is tack welded, safety wired (mid-hanger on subframe is through bolt mounted vs just bonded rubber). The refreshed fuel tank also has two straps from rear subframe to rear closing panel to ensure it stays in place! Fortunately, the Australian Van left the factory with underbody shields for brake & fuel lines and battery cable.
The rest is complete servicing of all suspension components...rubber boots are a quality issue and worry for steering rack, rack rod ends, CV boots, yoke boots.
A very practical issue is tools & spares...fortunately there are 2 LWB Classic Minis this year so we can split the extra weight as we both need to carry extra fuel on top...at least 6.5 Imp. Gal. on one long transit following a Stage out of Fort Nelson, BC headed to Yellowknife, NWT with some 300 miles plus on gravel.