Most of the time he spent on this project was probably in designing the case and hand-soldering the Atari 2600 itself, the latter of which is about a day's worth of work minimum (I think he mentioned spending a day hand-soldering the 2600 in this video or the soldering video, idk). Then he had to wait 27.5 years for the Replicators to finish printing the case, laser-cut the faceplate, test the 2600 to make sure it works (video, sound, I/O, the works), fiddle with the Battery Booster circuit, and put it all together while making adjustments on-the-fly. In no particular order, anyway.
Plus the soldering of the Atari 2600 itself, I'd say about a week, give-or-take.
EDIT: Lulzbot>Makerbot. That's the only useful thing I learned from FSF.