I bought a Le Creuset 5 1/2 quart French oven. I was reading the directions, and it said not to boil anything over high heat or use it in the oven above 350C. It said the enamel can crack or chip if I do that. Now how am I supposed to cook just about anything, from getting a sear on a roast to bringing soup to a quick boil prior to simmer if I'm not supposed to use high heat? Do any owners of Le Creuset enameled cast iron cookware have anecdotal comments about their experience, and whether they've had their enamel last successfully even using high heat? If so, I'd like to hear them, because I don't want to risk chipping or cracking on such an expensive piece of cookware, and I'd like to know how safely high in temperature I can use it.