Kenneth, do you temper shafts after you straighten them? I know the using heat to straighten them somewhat tempers them but I go back over each one, starting at one end and rotate the shaft over heat while working down towards the other end then lay them flat to cool. I still sometimes have to do a simple hand straightening(cold) but the shafts usually stay straight for me after that.
I tried a more aggressive tempering and I remember I messed the shaft up by causing long splits in it, and this was one that had sat around for years so I know it was dry. I then tried a lesser heat tempering more like what you are probably talking about but I could probably go more aggressive still than what I have been. Like you I usually bundle and straighten occasionally every few months that really leaves them straighter and more easy to work on
