You can store the private key or seed on a flash drive, but I wouldn't recommend it because such storage mediums can be easily lost or stolen. If you're willing to encrypt your drive and make a copy of it on another drive, then I'd say go for it. I usually encrypt my drives with Veracrypt to store all of my crypto seeds and private keys. It's a cost-effective solution that's often better than a traditional hardware wallet. Printing the seed or private key is also an option, but you'd have to be very careful not to lose the paper or let someone else get access to it.

Someone on the forum (krogoth) has been doing some tests by submerging paper wallets on water, so I'd suggest you check that out if you're interested. The great thing about Bitcoin is that you can store millions of dollars in the smallest place you can imagine, making it an extremely-portable asset/commodity. Not like Gold or Fiat where they take up a lot of space (depending on how much of them you have). As long as you have a backup plan to protect your Bitcoin, you'll be able to pass on your wealth for future generations to enjoy. Hope this helps.