So I will suggest you keep your private key safe by writing them and printing them out or putting them down on your Flash drive and make sure you don't share your flash drive with anyone so as not to be compromise.
flash drives are very susceptible to lose, we can't say that flash drives will last forever with me.. my personal experience, I accidentally lost my flash drive, so I don't really agree with flash drives.
my advice, it would be safer if you saved it in your other email which you never used to register on any site, then connect the email with your smartphone connection.