I have used Kongs for many years. My old Border Collie, Zak, never had food in his as he would never bother to get it out so it would just rot! He was not a chewer at all, but still had it to stay occupied if I went out. He would take it to the top of the stairs and let it go just so he could retrieve it. All day!
However, my little Jackiex, Buzz, got the top of his Kong in quite a short time. which concerned me. In response, I bought him one which is too large for him, so if he should get the top off this time, it will be too large for him to swallow, and if he kets bits off, they will only be very small. This is perhaps worth adding to the list of precautions for fierce chewers, as in real life, you are most likely to give your dog a toy when you are too busy to watch him and you want to keep him occupied.
Incidentally, his is rarely filled, as he refuses to eat most things except a home-cooked diet, which he won't entertain in the Kong, and I refuse to fill it with pate all the time! Too fattening! He does get it frozen with pate if I will be out for more than a couple of hours.
Always check ANY toy for signs of damage before giving it to your dog. No toy is completely indestructible, but the Kong range come closest in my experience.