Tyres for the Sahara and beyond

[Sapou]

Greetings to everyone,

My buddy and I are planning a trip that will follow the route from Greece via ferry to Italy, via ferry to Morocco, and from there all the way down to Bamako Mali. The first 4,000 km of the route will be mostly tarmac with the exception of a few (400-500 km) rocky pistes in the Atlas region of Morocco. Upon entering Mauri we will be dealing with a number of pistes (Nouadhibou to Atar, around the region of Atar all the way to the eye of the Sahara, and Atar to Tidjikja) and then while in Mali we will also follow pistes to and around Timbuktu. The total distance of the trip is estimated to be around 9,000 km (we are shipping back to Europe).
The bikes used will be a KTM 640 Adventure, and a KTM 690. We have been in contact with a number of people regarding which tyres would offer the best of both worlds (tarmac and off road that is). Once down in the Sahara we have narrowed down our options into using the Michelin Desert as a rear tyre, but are still skeptical about the front. One of the highest contenders is the T63, although we have read and heard mixed reviews about it, basically that it is really good on tarmac, but that can wear itself out on heavy off road use.

Note that both bikes will be loaded with alu panniers, probably a dry bag on top and maybe some extra fuel on certain legs of the journey. Also, we are still skeptical as to whether we should use more road oriented tyres (like the Metzeler Sahara, or the TKC-80) until Mauri, and then do the switch to the knobblies and dump the other ones. Of course if we can avoid this scenario that would be ideal, but we wonder whether the Deserts will be up to the task in Mauri if they have suffered some 4,000 kms on tarmac already (of course we are talking about max of 110 kph on the best of tarmacs, and lesser speeds on the rest)
Any advice as to the longevity (mixed mileage), behavior (both on and off road) of the above mentioned tyres, or any suggestions for different configurations would be more than welcome.

Cheers,

Sapou