Everyone have contributed with their opinions here and so far, I believe every important thing has been said.

Two points:

1. Don't trust flash memory. It is not good for long-term storage. The most durable is the HDD. However, due to moving parts that exist in HDDs, you shouldn't put pressure on them.
2. If you generate 50 paper wallets, you will need to backup 50 private keys. It is doable, but not the best choice.

Why don't you do the following:

1. Buy an airgapped hardware wallet, like blockstream jade, seedsigner etc.
2. Create a wallet, totally offline.
3. Make 2 backups of the seed phrase.
4. Store the backups in different locations.
5. Generate an address.
6. Save the address on 2-3 places, so you don't need to open the wallet again.
7. Send BTC to this address.
8. Repeat step 7 as many times as you want.

In 20 years:
1. Turn on your device, if it still works. It should have the private keys in it. So you can do whatever you want.
2. If the device doesn't work, you can order a new device from the same company and recover the wallet.
3. If the company doesn't exist anymore, you can enter the seed phrase in any wallet you want and recover the funds.

Bonus point: You can create a watch-only address in your mobile device so you can see daily that everything is ok with your hardware wallet.