I've read this book three times and just realized that the timeline doesn't add up.
In Part II, it has been 16 years since John Bergson died. Part I ended 6 years after his death, measured by the 3 years of success followed by 3 years of drought. Carl leaves at the end of these 6 years.
But when Carl returns, he says it has been 16 years since he has been gone.
Emil has also only aged 16 years since the start of the novel, from 5 to 21, so it isn't simply a typo at the start of Part II that could explain the gap being longer.
We spent the next eight months doing a bunch of things that he enjoyed, having fun together like we hadn’t had in decades. We went to Disneyland, his first time. We’d hang out at home. Torch was a sports nut, and he was very happy to watch sports and eat my cooking. He even gained a bit of weight, eating his favorite foods rather than hospital foods. He had no serious pain, and he remained high-spirited. One day, he didn’t wake up. He spent the next three days in a coma-like sleep and then died. The cost of his medical care for those eight months, for the one drug he was taking, was about $20.