Hi, and welcome from a fellow Louisianian!!

Your CYA needs to tested once a year if you're not using any stabilized products (like dichor powder or trichlor tabs) and not adding any CYA itself--but if you're using any of those things, or if you have a lot of splashout or backwash frequently, it needs to be tested more often so you can make sure you're keeping the right amount of chlorine in the pool. I find that in our climate, a higher CYA than normal works better for me, but it requires testing at least once a month to maintain it at the levels I like.