Fiiiiiiiiiiiiiiiiiine, I'll give you a measured answer. First play through, didn't rush imo, completed current content approx 250 days, didn't sleep alot from memory so 21min x 250game days = 5250 min ÷60 = 87.5 hours

As this is an approximation from memory I'd say you should get approx 100 hours into your game if you supe laid back