I'm a hoarder just like you. I buy decks and decks in the heat of the moment because they're awesome and just what I want right now! And then they sit languishing in the basket weeks later and I feel guilty. I learned to overcome that guilt when I acknowledged that I truly love Tarot and it'll always fascinate me. I'll keep coming back to it, and that becomes a passion I don't feel guilty about spending money on regularly.
And I feel that because of the huge varieties of decks, some Tarot users collect decks just so they'll have just the right one on hand for whatever mood they happen to be in. Sometimes your Old Faithfuls just aren't making the cut that day and you want to look at something else. I have my "theme" weeks or months where I see something interesting in life like, say, a documentary on ancient China, and then I become obssessed with reading and learning Chinese-themed decks for a while, and then something else overtakes my life and the Chinese decks are replaced by the new theme. While Tarot is a constant passion, I love learning about new things, and because my interests are so varied, so are my periods of focus, and so are my Tarot decks.
So I'd suggest to curb your spending habits, go back through your pile and pick one deck that really grabs you at that moment, and absorb yourself in it. Then when the feeling lapses over a few days or weeks, put it away and put a new deck in front of your eyes. Just make sure that you're constantly moving through your pile so eventually you'll explore them all to some degree. When you've gone through them all once each, for varying lengths of time, ask yourself if you can't rekindle interest in one of the first decks. Then when you see a new deck in store later, you'll have saved some money, and if you buy it and put it away, add it to the pile so it'll come around eventually.
Just keep your interests in flux, don't be ashamed to learn a bit of one thing to the neglect of others for a period of time, and eventually you'll find new decks might become Old Faithful.