I have no idea what his situation was. Some people do live to over 100 so it is entirely possible that he expected another 10 years and then died in is sleep (as happened to someone else I know who died at 63). If you get a terminal cancer diagnosis you might know you have 6 months or a year, but many people don't get that much of a clue (I know one person who was down to 2 weeks when unexpectedly his body fought off the cancer and he lived many years after)