Gearbox CEO Randy Pitchford has estimated Duke Nukem Forever's development time at between 6,000 and 7,000 months of manpower.
Writing on the US PS Blog, Pitchford said the linear shooter had undergone 3,500 to 4,500 months of development time.
By the time it ships, Gearbox will have added another 2,500 to that tally.
For comparison, Pitchford said Borderlands, generally considered a pretty large game, took around 4,000 months.
In real time terms, Duke Nukem Forever has famously been in development for fourteen years.
Pitchford is in a good position to know the game's history; he began his career at 3D Realms, working on a Duke title, and remained in touch with colleagues throughout the closure of 3D Realms.
"In fact, with the exception of just one person, every single designer and artist listed in the credits of the 2001 Duke Nukem Forever trailer had at some point either joined Gearbox Software or is now still a part of the project," he wrote.
Duke Nukem Forever releases on PC, PlayStation 3 and Xbox 360 on June 10 - except in the US, which gets the game on June 14.