I never have a productive six-hour unbroken stretch of work, but my partner will occasionally have 6-hour bursts of very productive coding where he stays in the zone and doesn’t notice time passing. He basically looks up and realizes it’s night and everyone else had dinner hours ago. But the rest of the time he works normal hours with a more standard-to-loose level of concentration.
I never have a productive six-hour unbroken stretch of work, but my partner will occasionally have 6-hour bursts of very productive coding where he stays in the zone and doesn’t notice time passing. He basically looks up and realizes it’s night and everyone else had dinner hours ago. But the rest of the time he works normal hours with a more standard-to-loose level of concentration.