How Many Copies of My Novel Do I Need?

Many, apparently.

I cleaned my desk so I could work on revising more, and here’s a peek:

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The stacked file trays are new, and I’m using them to sort feedback/different drafts of my novel:

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Top level is current draft, next my Alphasmart Neo, then supplies for revising, then feed back from an Alpha reader, then an older draft, and below it another older draft.

SO MUCH PAPER.

What should I be doing with my old drafts? It seems a waste to store that much paper, but I’m conflicted. What are your thoughts?