Apart from that , I will suggest you to take the periodic backup of your wallet.dat file and store in some other storage/device (other than the system where wallet is installed). It is also considered as a good practice.
Yeah great addition. I forgot about wallet.dat file.
Yes printing your keys on a paper will be the best solution rather than to save it on a flash drive. Why am i saying this, last month while i was in my room working thieves broke into my room and toke my laptop when the drive was connected to the laptop. Now i have lost everything, my little dollars is gone.
Every type of making our bitcoin wallets safe has it's typical risk. System vulnerability and the physical one.
I'm suggesting to save it on a flash drive and like what you are doing with the piece of paper, keep it somewhere that only you knows it.
That's just an option so everyone can have some options that suits them, all in all it still depends on how careful the owner is from printing private keys to paper and putting it to the right place / storage box.