I have 'worked' both a 19 hour day and a 21 hour day on separate occasions. The latter coming shortly after joking about 'that time we worked 19 hours'.

I assume you're suggesting it is impossible to do it regularly, which I'd agree with. The definition of 'work' also broadens profoundly. You will also pay for it by sleeping away more of your free time than you already donated to your work for free.