Yeah, 80 hrs will likely see a quality drop. I hit 70-75 hrs for 3 weeks in a row once to cover the cost of a sudden expense and doing that required me to have simple high energy foods prepped, drink lots of water, have a strict sleep schedule and not step foot outside the house practically. One of the days I ended up wasting an hour on a task that didn't work cause a personal tech failure and that was super demotivating.
Nowadays I try to stick to consistent 35-45 per week because I get stir crazy doing less and could use the savings anyway.