Don't worry man, I put my baby boy down a few weeks ago, had arthritist in the legs because of his size, and breed they would only last 5-8 years simply because their bones get worn down from the sheer size of the body...here is a picture.
name was leeroy, was 5 years old, this is my 4th Saint Bernard, he looks fat but his about average for a male..."80-120KG"
I've got some more of my other 3 who are going good, they sobbed and were depressed when he was gone for a week or two.