I actually run a biz that produces hand made GLUTEN and it takes ATLEAST 2 hours to bake it. If it is too soft, it doesn't have enough water (trust me) just add, and add, and after the time has elapsed you will see the toughness emerge. Baked Seitan gets softer BEFORE it gets harder. Keep baking, keep adding liquid. TIP, don't just add clear water, as this will dilute the flavours you added to the gluten, add seasoned water, HEAVILY salted water will actually help prevent too much diffusion of your flavours out into the cooking broth. And be sure that there is some OIL in the water too! Like 1/2 C for a large pan... Ok there are all of my secrets.