I changed the 500W halogen bulb on my pool light with a generic heavy duty bulb T3 from HD and since, every year, it kept going out. And it wasn't the bulb that went bad but the contact at the 2 ends that hold the bulb. I had to sand out the deposit and reinstalled the old bulb and it work for a about a year and repeat the process. I am not sure what caused the deposit but I think because I didn't let it completely dry out before putting the seal back and the moisture got on the metal parts where they hold the bulb. Or may be the lube material from the gasket is water base? What do you think?
Also, What is the common suggestions here for LED fixture. I am thinking Pentair white LED but I am not sue if there are better choices. The existing light we have now is a Star-Rite Sunbrite 05509-3015-3050, by the way. Pentair doesn't list the dimension on their light so I have to find the info somewhere else.