I feel the opposite is true. Working longer hours actually reduces my level of productivity because at some point I start making mistakes that take time to undo. For me that's only about 6 hours of coding; if I work 12 hours then half of my time is spent undoing mistakes or finding better solutions, so I'm less productive than if I'd only written code for 6 hours in the first place. I definitely don't find that I'm more productive if I just put in more time ad infinitum.
I feel the opposite is true. Working longer hours actually reduces my level of productivity because at some point I start making mistakes that take time to undo. For me that's only about 6 hours of coding; if I work 12 hours then half of my time is spent undoing mistakes or finding better solutions, so I'm less productive than if I'd only written code for 6 hours in the first place. I definitely don't find that I'm more productive if I just put in more time ad infinitum.