I think Francis's experience is a perfect example of how you treat your bike/motor - will have an enormous impact on it's longevity.
If you're mainly trail riding and touring (in all sorts of conditions), presumably not having pedal strikes too, but taking it relatively easy compared to DH - you can expect great longevity - even from a Shimano motor. It's like the Bosch motored Cargo bikes which go on without problem for 50,000 miles. (I'm still waiting for him to do some saddle reviews as they must be pretty well tested !)
A huge variable on "reliability" will be the rider and where and how they ride - then add in if they're a a quick draw on the jet wash and you just throw in more variables.
Then you have the whole flip side to it .. which motor can I get repaired.
Ironically, the Brose motor, which sold in vast quantities in Levo's and Kenevo's, doesn't really have the best reputation on the reliability front. But due to the large customer base and the issues, there's now an excellent third party support infrastructure in place to get your motor repaired.
The Brose is quiet, powerful, efficient, when used carefully - reliable and you can actually get the thing repaired !
I say ironically, because it's ultimately led to the situation that the bike you buy new, which maybe didn't always have the most stella reliability record, is actually probably one of the safest bikes to buy second hand - because of that very reason !
