Eternal was 3 years. I think Rogues was about the same. Granted I probably could have written both of those in much less time, but real life and all. Slowing down, getting older, getting distracted, etc (The Struggle)
But really I've never been too overly impressed by word count for a story, I've always believed a story is as long as it needs to be, whether that's 600K or 9K. Granted the longer stories do have an advantage since there's more potential for a more complex plot, more choices, etc. but there's also the chance of them just being boring slogs.
Northwind's story for the Grimdark fantasy contest comes to mind which was 100K and just sort of went on and didn't grab me, while Malk's ended up winning since he hit all the important points in just 27K.