I was wondering if there are any security or privacy implications I might not see when I want to use only one Bip-39 seed to derive a mainnet and a testnet wallet from, using the testnet wallet to practice and remember the seed by heart and the mainnet derivation for real funds.

Obviously one must be equally careful when entering the seed words, regardless of using the testnet or the mainnet wallet, against side channel attacks. But anything besides that I'm missing?