Does Flex Seal stop leaks?

So, I've heard a lot about Flex Seal and its ability to fix leaks, but I'm still a bit skeptical. Can you tell me, does Flex Seal really stop leaks? I mean, are there any instances where it hasn't worked or has failed to seal a leak properly? And if it does work, how long does it take to set and cure, and how durable is the seal once it's dry? I'm just trying to get a better understanding of the product before I make a purchase.