These are presta tubes on a racing bike. 23c in front, 25c in rear. 105 psi in front and 90 in rear.
Thanks for your reply. You are making me think I might have mixed together period 1) valve base failure when I was over-tightening the lock nut and period 2) other problems at or near the valve base after i stopped over-tightening the lock nut. I may not have had so many problems during period 2. I don't remember. So, at this point, I'm inclined to stop worrying every time I yank the floor pump chuck off the valve. It may simply be NOT a problem, after all...