My buddy slept on a Sleep Innovations Shiloh 12" for years. He got married 6 years ago, and bought a new Shiloh in 14". His old one was given to his brother. Both are still being used.

BUT - neither my buddy, his wife, or his brother have back problems, neck problems, they are all fairly short and light, and have narrow shoulders. So... none of them need good support or contouring. Your mileage may vary.