In the last couple of years I started increasing my time on the long string and for me I get less set.
Interesting observation Steve. Perhaps the different results can be attributed to differences in the way we implement the method? Would you ever pull to full design weight (on the longstring), to bring the stave to brace height? How far do you find yourself drawing out the bow on the longstring?
IIRC, I did some calcs once that indicated bending a stave to brace height with the full weight and with stiff unreduced limbs can overstress the center third of a bendy handle. I was suspecting that I had damaged the wood on a bow I was tillering. Not to the point of creating permanent set, but the slow-to-return hidden damage kind of temporary set.
Like Will and Del, I do not bend a bow much past brace height on the longstring, but I do reduce the weight I use to get the limbs back that far, if I am still making adjustments to tiller. I actually try to bring the bow to brace height with less than full weight, in order to leave the center third less stressed in the early stages of tillering.
Personally I feel that the longer a bow is "tortured" on a tiller, drawn inch by inch and "exercised" the more the wood is being taught to prefer being drawn than being straight which is of course the opposite of what we want.
I agree Will, at least for bows that are my own, and I can make tillering adjustments to, whenever needed. For a reliable shooter to be used by another, I tend to exercise more as I go, and guess what I end up with is basically an overbuilt bow.
I have never considered that the "torture on the tiller" method is necessarily part of the long string method per se, but both are often presented together in some tutorials, so I can see where one might think they go hand in hand.