I've worked on secondment in remote locations and easily passed 80 hours per a week. Four weeks of straight 12-hour shifts + up to 2-hour overtime daily. Probably averaged 70 hours of effective work and genuinely approaching 100 hours in some 7 day stretches. No meals to cook, no chores, no commuting. It was actually far easier to stay motivated and focused, I felt 20 again. I would be lucky to average more than 4-6 hours productivity in my day job though. Don't underestimate the influence of environment and incentives (amortized it was only about 50-60 hours - bankers/lawyers are probably working in bursts too though).