Why don't you just use BIP 39 passphrase, then save the seed words on crypto.txt without the passphrase itself?
Most wallets do not offer that possibility, they generate a 12, 15, 24 word wallet for you. Of course using TREZOR/Ledger with a passphrase is safer, but you could even use that AND date-shift encrypt it for EXTRA security.
I agree that there aren't many wallet which let you add BIP 39 passphrase during word seed generation. But when it's available, it's easy to use it.
IMO 7 days is quite short since he use free (?) API and single-thread software.