Ohohoho, here's a good one.
So, when I turned 6, my Mom got me Pokémon Yellow for my birthday. I was crazy about the cards and the anime, so the games were the next thing for me to become addicted to.
I've posted this story about 264534 times on this site now, so I'm going to cut it short and say it took 4 years to complete Yellow, entirely because of my on/off basis of playing it. :P I at least completed Gold in this 4 year period, became addicted, and didn't play Yellow for a long time.
So it's not that it took me four years, it's just I took a lot of long breaks :P