URI bulbs - max 6 months. All bulbs change spectrum and deteriorate with use. Sometimes they burn out completely by then. The company rates them for 6 months for reefs according to their fine print. Its not worth the coral loss by keeping them a year unless you don't keep any sps. In the medical field, we set a timer on the bulbs and when they hit their max useful hours, they're disposed of. We have very good lamp sources for instrumentation, but, they get changed on a regular basis because the spectrum goes out of useful range. Though sps can adapt, sooner or later they will get to a point where they can't thrive and when thats reached, mortality rate sets in on the colonies. Change bulbs every 6 months if you keep sps and never live to regret it. Waiting too long means troubles, bleaching with new bulbs and so on, even with mushrooms as they all adjust to the light source.