I only have last one,from those here, white lego technic car.. all others i build from instructions...i spend a day/two, maybe even more for each model..all depends how difficult model is.. ( when i'm "in the mood" for modeling, my wife doesn't love me then )

Yes, i build every piece as component and then i build everything piece by piece... and yes these are existing LEGO kits..
although i'm 26 y old i still love lego toys...
here are some more pictures

Some of my works in Sketchup