Now THAT is a GREAT question!
One which I cannot answer, honestly.
I often wonder how this time is calculated. This is one reason why I don't calculate it. I suppose I could log all time spent in the garage, but I spend time in there just looking at the plans and holing parts in the air. They need airing out from time to time.
I just do things when I have time and I am certain that they go that way. I seem to be a slower builder than Dan, but isn't everyone?
If I were to venture a guess, and that is all it would be... about 25 per month would be close. Of course, that is a variable.
Lemme see, at 25 per month, and a 2,000 hour build... that comes to... (drum roll please!)...
80 months or 6.6666666 YEARS!!! Looks like I need to step things up a bit!!!

CJ