I've heated up to 3 times after reading some other advice. Inducing reflex after floor tiller I give it the hardest treatment, then at mid-tiller, and a lighter treatment just before finish. Using hickory, I like this method, but I don't heat treat all woods I've used.
Let it set still for a day before stringing and flexing again, I think that flexing too soon after heat is more likely to cause chrysals, with the wood being less hydrated.
You can heat treat to basically a blackened state but don't char the wood. When I first started I wasn't treating it near enough.
Good luck!
