Hard to say. Usually within 12hrs but I've heard of them still being alive several days later and not recovered because they were still spry enough to get away. I'd suppose it's not impossible for one to survive, given the severity and its ability to fight the infection. That said, a gut hit is the most lethal hit shy of blowing out a heart or brain. I've heard of outfitters instructing hunters to shoot mid body because they have 95% success rate of recovery on gut hit deer, apparently better odds than aiming for vitals.