I can say I've done a few 72 - 96 hour stretches of near total wakefulness (power naps of 20-40 minutes as possible, food and caffeine available nearly any time

I can say I've done a few 72 - 96 hour stretches of near total wakefulness (power naps of 20-40 minutes as possible, food and caffeine available nearly any time) but there's definitely a feeling of disconnect, being separate from the senses and just floating inside my own head toward the end of those. We're talking full up tactical exercises in the military, and a couple of critical repair scenarios here and there since. A couple of days of near total downtime is a minimum to reset from that kind of effort, and 'normal' work for at least a week or two if possible.