How can do you extend the life of your tubes?

Great follow up question, Warrenh. I'd wanted to get a tube tester and did talk do a couple of electronics techs with units for sale. Those discussions were not real helpful. They were very non-commital on whether a tester (and talking some of the better regarded vintage units...think Hickok) would do what I was hoping; i.e., warn of a tube going bad or that needed replacing. Kind of left me scratching my head and I never did invest in a primo tester as a result. I guess I could ask the audio dealer I've done business with to test them on his unit for a fee.

Thanks, Mark. Helpful info. The other thing I was hoping to be able to do was match tubes so if I had a group of, say, EL34s of the same brand but with different histories, be able to put together a quad that could be managed by my amp's auto-bias circuit. I believe if tubes are too mis-matched auto-bias can't compensate...apparently not good for the amp. Is matching something a tube-tester can be used for?? Happy to be corrected on this issue.

Warren - apologies for hijacking but hopefully this is at least somewhat related to your question; that is, having a reliable piece of test gear would keep you from unnecessarily tossing tubes that still have some life in 'em (assuming no audible degradation in sound quality).