I've messed around with some of my hickory bows in a similar manner and discovered that I could fix string follow in a bow that had never been heat treated before. I recall one that had about an inch of follow, where I heat treated 4" of reflex into the bow, which brought the draw weight up enough that I could re-tiller the bow back to the original draw weight. After shooting in, this bow retained about 1/2" reflex and had a much better full draw profile. However, when I attempted to re-heat treat it back to the 4" reflex, I had to re-adjust the tiller a slightly, and it pulled right back to the 1/2" of reflex, but I did gain a couple pounds of draw weight. I think the only advantage I got from the second treatment was to deepen the effect on the spots where I had removed more wood adjusting the tiller. This was a straight limbed Eastern Woodlands style, and I had similar results with a Sudbury I made this past summer. I messed up a bit figuring out how to tiller that style, and was able to recover it through heat treating and re-tillering, then heat treating again where the wood was removed, then fine tuning the tiller. It does seem, from the first experiment, that heat treating is a one time thing, unless you remove a sustantial amount of belly wood and lower the draw weight.