"time it takes to hew an 8" by 8" timber from scratch"
It would take me longer to hand hew the above log than what Mark says he can do it in, but then he might be using a chain saw to cut vertically to the line prior to hewing, that I don't know.
For me using the scoring axe to rough score the log prior to hewing will take more time, also I make two passes on each side a rough hewing pass to within 3/4" of the line, and then the finishing pass scoring at 3" to 4" intervals, then removing the scored material right down to the line. Done properly it will leave a surface that shows the bite of the axe at the closer intervals, and once in a while you might see the rough scoring mark at a wider intervals. A good hewer will produce a surface with very few of the scoring marks visible, and to produce an authentic hewn surface you have to follow each step faithfully without skipping any of the above steps. I estimate it would take me 2 hours or about 30 minutes per side to produce an 8" by 8" timber.
I realize that many of you will likely turn to the chainsaw to help speed up the process, or "veneer" skim a sawn surface as suggested above but it is unlikely that you will produce the kind of surface that passes a close inspection by a knowledgeable person. If you are satisfied so be it it is your call, but in closing I will only say that you should at least know the feeling of having completely produced a surface using the basic tools available at that time, that way you can compare the differences in the finishes of the two produced surfaces, using different methods.
Also there is something about a hewn timber that makes it unique, the variations in squareness, the slightly larger or smaller measurements all along its length, and sometimes slight windings,a few axe marks here and there, little chunks of wood that were dislodged by the strike of the axe(s), these are the things that make a hewn timber beautiful to look at and contain your signature.
Thanks for all your great comments, and those beautiful pictures of your axe collection Mark, thanks for putting them on!!