I remember reading an article about British workers during WW2 who were willing to work any number of hours to beat the Nazis. Initially their productivity spiked as they worked more hours. Eventually it crashed, and they did a study to identify the most productive number of hours. 35.
I remember another article from a Harvard business review where they studied the number of hours worked which was correlated with the highest promotion rate in business. 45.
So, if you’re riveting airplanes, or other manual work, 35 hours per week seem to be maximal. For office work, 45 hours per week at least gets you the best results from the business noticing your effort. I shoot for 45 hours a week on average, but sometimes go as high as 80, when sprinting, and as low as 25, when trying to recover from those sprints. Seems to have worked well for my career and work/life balance.