We took our two 650 Dakars through Africa and most of South-America, plus some training in Morocco: more than 50,000 km each. The only weak point we found was the suspensions. One broke down at the end of Africa. Shortly after, the other started to leak but only when parked on the center stand. Both were replaced in South-Africa under guarantee. Last month in Bolivia, we exploded the oil reservoir of the rear shock on on eof the bikes, and it was fixed today in Lima for only $50 (instead of $800 to change the suspension as any dealer in Europe or the US would have asked us to do).
Besides that, hardly anything. The direction wheel-barrels of one bike where changed in South-Africa by safety. A wire had to be reconnected in the fuel pump. I think that´s it.
About the suspension, the problem could come from the fact that we took som every bad roads and our bikes are heavily loaded: Touratech tanks (around 15kg + 22 liters of fuel), panniers (15kg + 15 of luggage) and bags (10 kg easy).
Overall, especially when we compare with the problems that every single other rider we saw in Africa encountered, we think that our bikes behaved amazingly. However... we later met 2 guys with 650 Dakars who were not so happy. One had broke his suspension too (again plenty of off-road), the other had a leaky fork and changed his battery 3 or 4 times.