Watch an airplane being built in one week at EAA AirVenture Oshkosh 2014.
Via Iaman, who says "....and I thought it took 10 years to build your own airplane." It might take you ten years of elapsed time, but these guys probably invested as much time and energy in building this one. It looks like you've got at least 50 people working on this thing, 24 hours a day for 7 seven days. That comes to 8,400 man-hours. If you spend your weekends for ten years building an airplane that also comes to 8,400 hours. (8,320 actually. Close enough .)