Maybe they have been in use maybe the havent im not sure but the guy also gave me a bucket of salt... from 2014 so i presume he had the reef stuff sitting in his basement for a few yearsI’m not sure that would be the case in this instance with the bulbs being over a decade old, and presumably they were in use for years?
But for coral keeping purposes you are correct. The loss of the desired spectral output is what indicates when it is time to replace the bulbs. Changing T5 and MH bulbs is done to keep the proper light available for photosynthesis. The bulbs will continue to produce light but the spectrum is deteriorating.