After watching some videos of the recoveries and salvage that SMIT Salvage and Mammoet have done, there's only three obstacles to recovering ANY vehicle in ANY environment - time, money, and effort. Any sufficient application of 2/3 of those should get anything unstuck. I highly doubt anyone here is driving something to such a place that it could not be recovered from, unless they somehow push it into an active volcano. A mechanical breakdown is rarely, if ever, so severe that the vehicle couldn't be fixed where it sits, parts and time allowing. Getting something so big so stuck that it can't be recovered is also pretty unlikely, though I imagine there comes a point where it becomes insurance's problem to cut it up and haul it out - I'm picturing something like an Earthroamer HD over the side of the Bolivian Death Road in that instance.