Hi...answer is a little bit "it depends". What kind of tube? you can usually google the typical time of wear...3,000 hours for some,,,20,000hours for the longest. Or ask your manufacturer/dealer. Then do the math...how many hours have you played them? Then do the listening test...you tend to hear a slight fuzzing over of your mid to uppers, or the power just does not seem to be there...not as solid imaging. And of course, when you replace tube, it is instantly back. good luck
