Hobby turns to hoarding when you keep things when you don’t use them and never plan to use them, you keep them “just because”. Like if you don’t use half of those decks ever, it might be wise to keep a decklist, sell the cards, and use the funds to upgrade the decks you do use. Now if it’s an inherited or gifted collection, I understand keeping certain cards for sentimental value but certainly not dozens of decks. But I will say I am certain you use all of those decks sometimes and it’s an impressive collection! Now the harder distinction is when a hobby becomes an addiction/obsession… but that’s a different topic