An 18-word mnemonic phrase increases protection by introducing more words for the sequence. Here’s an case in point: This extra complexity improves the hazard of misplacing the passphrase, and thus losing your copyright. One more idea that further more simplified the backup of your wallet seed was proposed in BIP-39 https://thefairlist.com/story9572335/the-ultimate-guide-to-bip39-seed-phrase-github