Why are some beans only available for a "limited time"?

為甚麼有些豆子只能「期間限定」?

The coffee expert working with Doudou has some influence in the industry and has been a long-time friend of green bean suppliers. Therefore, whenever there are top-quality, in-season beans, he always manages to get them first. And I, this little bean, am fortunate enough to get a small share from him to share with everyone. So, some beans are truly rare and hard to come by; there's only this much, and once they're sold out, they're gone. If you want to taste them again, you'll have to rely on fate.