In the winters of 2013-14 and 2014-15 I did two trips of 4000 km+ in India on the same set of Schwalbe Marathon Mondials. This last winter 2015-16 I cycled again in India and would have used those same tyres once more had it not been that I bought a new bike that takes 28" tyres.
I have seen several reports of people getting both 10 and 20 thousand km out of their Schwalbe Marathons.

I do however carry a cheapish Chinese foldable tyre as a spare, just in case.