The last thing I recall seeing of him was a 60 Minutes interview done in the mid 80's -not long before he died. You had the sense that all the booze and smoking had produced the expected result, and it seemed he wasn't that happy. Which was unfortunate given all the laughs he had provided.
It seems a number of comedians that make so many laugh, are, in the own personal lives, very unhappy people.
Supposedly Edmund Kean the great early 19th century English actor said this on his deathbed, “Dying is easy. it’s comedy that is hard”.