I learned French in school, and then later I spent a summer in Quebec where my fluency was cemented. It helped me pick up Spanish because they're structurally very similar, and both based on Latin. I'm not yet fluent in Spanish, but I live in an area with a very large Mexican population, so I get the opportunity to practice and use it pretty regularly. I could probably be fluent in 6mo if I focused on it, but I'm lazy so I just pick up bits and pieces as I go. I anticipate general fluency in the the next 2 years. If I hadn't learned French, I don't think I'd be anywhere near as far along as I am.