I have never used this as a controller. I purchased it at the end of last year. I bought it because I couldn't do the initial setup of the Switch本体 without Joy-Cons, and I inserted it into the main unit once for the initial setup. I only used it for that, and I have never used it as a controller. To prevent damage to the built-in battery, I charge it once every few months, and I have taken appropriate measures to prevent the condition from deteriorating. I believe that the main unit, as well as the battery condition, is as good as new. Thank you.