Dressed weight x 40% is the standard formula for boneless meat yield. So you're both right on if fat was added.
I recall the thread where the time required to process a deer was discussed. I think a lot of the guys said they process their deer down to larger pieces. The trim/grind pieces were just frozen. That's what I do at least.
If I accounted for all of the "final" processing such as removal of all silverskin, slicing roasts into steaks, grinding, etc. I'm sure it would add up, maybe even over 5 hrs. My main objective when processing is get it skinned, cut up and wrapped and into the freezer. That generally takes less than 2 hrs. Larger pieces keep better in the freezer, and silverskin is easier to remove after the meat has been frozen. I find that meat grinds much better if it is still partially frozen.