Madrid, Spain to Moscow, Russia (41 hours)On top of the physical distance. You WILL have to stop for fuel, food, relieving your bladder, and stretching/walking around even if you do ZERO tourism along the way. Minimally, this will be once every day of your trip for 15 -30 minutes. Most inexperienced road-trippers also don't account for the reality that a long road-trip will likely take it's toll on you physically - especially if you do something other than sleeping on someone else's driving shift.
Santiago, Chile to Rio de Janeiro, Brazil (43 hours)
Shenzhen, China to Harbin, China (37 hours)
Perth, Australia to Sydney, Australia (40 hours)
1 full days spent at each major city seeing the culture/vibe and major landmarks
1/2 day for each major museum
1 full day each for large National Parks, Amusement Parks, festivals, etc.
1/2 day for each mid-size city
1 day per week for unwinding, catching up, or unplanned activities