I'm always cynical when it comes to beauty product claims. I figured 24 hours was marketing speak for 6 hours if you're lucky. This product really lived up to it's name! I've been using it for over two weeks now and yup, 24 hours is right. My cream, gel, pencil, and powder liners have been put tho the test with the primer. They look just as good as when I applied them at 6 am as when I washed them off at midnight and there were a few times where I fall asleep before washing my face and yup, 24 hours later my eyeliner did not budge and I had to break out eye makeup remover to get going for the day. My powder shadows didn't crease either. The other thing I'm trying to figure out is how to blend shadows while using the primer. That primer really locks that powder in there and it's been difficult of me to blend, but I'd rather have eyeshadow that stays put than perfectly blended eyeshadow that's out the door four hours later.