I don't know if this will be an alternate future or the main timeline, but here is a pic about Monty Burns' death.
Like 15 years later they finally went a couple, sharing many things together, the unavoidable happens.
That night Burns is too old (more than before) and very weak. Finally he'll die for oldness. His faithful assistant Waylon Smithers (around 60 years old) is next to him, wainting for the end. He's so sad, he wanted to avoid that day for many years, even Monty himself tried to save his own life countless times... but he realized that it will be unfair that he (kinda) live forever while his dear Waylon is gone someday. He simply will cannot resist to lost another Waylon.
His life was meanless but when he share this feeling of love for others in his life, that is more important than all the money of the world and the eternal life. So this time he'll accept death with a smile.
Before he passes away, Monty said many things to Waylon, so is watching at him non-stopping. Things about how much he loved him, about how grateful of meeting sure wonderful people in his life; like Waylon himself, his son Ryan, his own son Larry, John Smithers, his own father Clifford, his dear friend Waylon Sr.
"You really have your father's eyes...", that was his last words.
Waylon Jr. never knew, not in the very end, that Monty never stopped to love Waylon Sr. But sharing his love for Smithers Jr. gived happiness to his life once more.
C. Montgomery Burns and Waylon Smithers Jr. (c) Matt Groening