To quote Indian Jones:
"It's not the years honey, it's the mileage"
I watch videos of Mark and the whole band from the Brothers In Arms tour, and he is absolutely drained near the tours end, they gave it there all after such a long tour, one of the longest ever by any band, so, I am not surprised he has ended touring, he did do a lot of it over his long career, and he is in a very lucky place to be able to make that choice.