I have been using this product for a decade or more, and it just gets better with each improvement. My first dental guard was custom-made by my dentist for a lot of money ($100s, as I recall), and it lasted maybe a year. I decided that was way too much to pay, so I got one of these for around $20. I can now use them for over a year before they wear out. They fit tight and don’t bother you at all when you sleep. The formed part does eventually detach from the the flexible plastic outer guard, but that process takes months to complete, and you can still use it till it completely separates. The key is to brush it thoroughly every time you brush your teeth, so it stays clean and sanitary. You can ignore the "don’t wear any longer than 6 months" advice, unless you have some peculiar dental problems. I don’t, other than bruxism (teeth grinding).One tip: before you heat the new mouth guard and insert it into your teeth, practice a couple of time to make sure you align it properly. I heat it on the stove in water rather than using the microwave, just because I trust that more.Second tip: when you’ve heated the mouth guard properly (follow all the instructions), and are ready to stick it in your mouth, don’t bite down too hard and also leave just a little bit of room in front of your front teeth for some of the silicone to remain there as you bear down with your bite. If you bite down too hard you will hit the flexible plastic outer guard, and that will weaken the bond of the silicone to the outer guard, shortening the life of you mouth guard considerably. Remember that most of the grinding and wear come from your back teeth, so you want a bit more "cushion" back there than in the front, so think of biting down with more pressure on your front teeth than on your back teeth. I know that sounds weird, but practice it a little, and you will see what I mean.Third tip: once you have bitten down on the new mouth guard, maintain your bite until the directions say to let loose, and very slowly remove the guard from your teeth. It will want to stick at first, and you don’t want to yank crowns off as you remove it. If necessary, swish a little water around in your mouth and then ease the guard off your teeth.If things don’t work the first time, you can try one more time, but the mouth guard will probably not last as long or fit quite as well, so get it right the first time! Practice!