So I finally got in touch with the ebay seller - Hanshare electronics. I asked for him to elaborate on the conditions of the 1 year warranty and asked if there were any tests done to the tubes after factory testing. Here's his response:
Dear Valued customer,
please kindly note the quality warranty will make sure the tube will be matched and work smootly in one year. anything that make the tube not working as it should be ( for example noise) or unmatched, it will be covered. buyer need to be responsible for all postage that include sending back to us and we send repaired one or replacement to you. but obviously please understand if you broke the tube and not a vacuum one anymore, it will not and cannot be repaired. basically, if you care about the tube, nothing will happen.
sorry we mean technical data sheet will be sent together, it was checked by shuguang factory themself who are so professional in this field.
Best regards
Ricky
So it seems that every possible failure except vacuum loss is covered by this 1 year warranty. Me likey! I wish other manufacturers of tubes would follow suit with this. I'm not so thrilled, however, about Shuggy's testing being the only testing/matching process. Personal experience in this regard has left me questioning their quality control and testing methods. Still, I may take the plunge on a quad in my future.