You can heat treat anytime you want even a month after you finish the bow if you want. I prefer to heat treat and put my reflex in right about the time I am ready to brace the bow. Not much wood comes off at this point. I don't heat treat in sections either. I run my heat gun back and forth over the entire limb, I figure it gives the heat a little more time to soak in. I also never go for a brown color, at a certain temp the yellow on osage will darken just a bit and get deeper and less bright. This is about where I stop assuming the back of the bow has gotten hot enough I can't hold my hand on it for more than about a second. This lets me know the heat has soaked all the way through.