Canada

I've done that - I was in construction and we had one house with 10 foot walls which are not standard. It was faster than the windows, sillplates and the like - but not by much. We don't have a miter saw on the truck so it was even up the ends, then measure, snap a chalkline, then cut 1.5 layers. Then move that second layer by enough to not cut the layer below and finish the cut. (you cannot continue down the stack as errors accumulate) Windows and doors are standard so after some time I just knew the most common sizes - I did have to do some works for the odd sized windows.