I am so sorry about Mende, but if he is not in any pain then that is all that matters. I would have cried too, but maybe on Monday you will get good news, I hope so.
I have always heard they live to be 50 to 60 years, so this is a surprise to me, 35 to 40 years is a bit less than we all realized, but if this is what your vet said then it must be factual.
Please update us on Monday, we are anxious to know what you find out, but I know Mende is receiving all the love and care from you that he needs, he couldn't be in better hands than yours.