Just an update on this thread.
The tandem team in question has now logged over 8,000 km, Buenos Aires-Argentina to Sao Paulo-Brasil, and Capetown-South Africa to Syria (minus flights from Sao Paulo-Capetown and Tanzania to Egypt).
Deore hubs have so far survived, LX brakes without a drum have held the loaded tandem (except for one descent in the rain were the pads melted).
Mavic 138 26" 36 h rims however did not make the trip, rear rim was replaced in 1000 km with a local Argentine rim that is still on the bike, and front rim was replaced in South Africa with an Alex rim, also on the bike now. However some spokes have broken along the way, and as TG sugested, they did eventualy need to have a casette removal tool shipped to them. Continental Sport Contact and Schwalbe Marathon tires have done about 2000 km each on the rear and 5000 on the front. The rest of the trip was done on localy sourced tires which would last 300 - 800 km
You can read more details here (in spanish):
http://elmundoentandem-elequipamiento.blogspot.com/
So far it is the triumph of tenacity over what we in this forum might consider inadequate equipment!