I think the day the eggs will hatch varies by incubator. Some incubators distribute heat more evenly and at a more constant temperature. Incubators such as those would have a faster incubation time vs an incubator that didn't distribute heat well or evenly. I'm only going based upon what I know and what I've been told by other breeders. But every incubator is different. His eggs might be completely fine coming out at day 49, but I wouldn't suggest cutting until the first egg pips. Just my standard.