Fischer beat Spassky in Rejkyavik in 1972 for the World Championship. This took almost 3 months (July to September) and there was controversy, disagreement and negotiation about where and how it would take place. This had the backdrop of being a Cold War proxy too of course.
Interestingly, Fischer didn't play competitive Chess after this. He was set to defend the title against the eventual challenger, Anatoly Karpov, in 1975. Fischer too didn't like the tendency for draws and proposed a format of first to 10 wins (with Fischer retaining the title in case of a 9-9). This was rejected and Fischer ultimately abdicated and never played competitive Chess again. He also became a semi-nomadic recluse too.
But it also wasn't Fischer's first hiatus from the game. There was the 1972-1975 gap but also anotehr in the 1960s. He clearly seemed like a troubled guy.
I've always found it fascinating the level of commitment required to play Chess at this level. I certainly have never had any interest in that (nor the ability, to be clear). No one really seems to know how to solve this without going to a more blitz like format.
Chess at the highest level seems to revolve around memorizing a whole book of openings and defenses while being able to take advantage of mistakes but also finding novel approaches in standard openings and defenses but now it seems you have to go fairly deep into a game before you go off-book.