All joking aside. Donkeys live a long time I guess as do dogs.
When my brothers Great Dane of thirteen years (way longer than the average of six to seven years) died I was beside myself with grief. I had lost a friend that I had since the early nineties.
It's a big deal for him I'm sure & I hope he gets through it because it's NOT easy. OK it's not a human death but when you get attached to a donkey/dog for that length of time it's a HUGE blow when they die.
The best therapy may be to get another donkey. My brother got another dog....A Great Dane.