I actually collect 4-leaf clovers, and have gotten so many over the years that they are a little bit commonplace to me. That’s why I have a pretty big collection of them now just rattling around in a box somewhere. And for the most part, they’re still good.
On the day I picked them I would press them in a book. After a few days I’d take them out, and they’d be flattened and dried for all eternity.
I’ve kept them in envelopes, in boxes, and loose in drawers. I’ve kept them for years and years. They just do not “disintegrate”, unless they are handled roughly. It’s the friction that breaks them down, not just age.