@jimbones I didn't read the whole thread so I apologize if someone already mentioned this. I had the same problem. My phono stage needed the tubes replaced yearly and then I got a tube headphone amp and was going through tubes every 3 months. The problem was the voltage was high, which fried my tubes. I got a $20-30 voltage meter to confirm the voltage was above 120. It was not much above 123 - 126, but that was enough. I get a step-down transformer and that solved the problem. I hope this helps.
Mike