Use Archival-Quality paper and ink for seed phrases.

If you write down your seed phrase, use archival-quality paper and ink.

Post-it notes and other papers have acids that cause them to break down. Non-archival inks fade over time.

So keep some archival supplies at your desk. It's cheap and easy to do. Transfer your current seed phrases and private keys to archival formats.

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Or you can engrave your seed phrase in metal, or store it in secure offline digital keychain, or carve it into wood, or cast it in ceramic.... point is, you need your seed phrase to last for decades, so make sure it's written in a sturdy format.