It varies by individual how often they moult. Some budgies have two to four miserable moults per year, while others may have less severe moults once a month. On the other hand, some have a combination of both. My budgie falls into the last category. As long as he's getting a varied diet and is healthy, there's no reason to be concerned! Additionally it seem like your little one is on the less frequent side of things if his last moult was February!