I think that if I had focused and been able not to do anything else, I could have finished my last ARF (Seagull SpacewalkerII) in about 8 hours. Now that's if I hadn't used gold'n'rods, changed the alierons to 2-56 h/w, made a few mods and had to cut out covering to install braces. And of course that dosen't include epoxy cure time, varnish drying time, etc etc. I put my WM SS 40 together by the book, mostly, and I think it took me all of about 12 hours, but I spent a lot of time sanding the engine mount to fit, and I like to "measure twice, cut once" only I do the measure part twice. I wouldn't take the build time too seriously, and certainly not as a challenge.
But to contradict myself, I think that I could have had my Avistar at the field within an hour of opening the box, actually with some experience 30 minutes would probablly have been doable.

Andy