A paper wallet doesn't have to be a single private key, it can also be a master private key or a mnemonic. Nowadays all the bitcoin wallets are HD and they support BIP32 and BIP39 (or an alternative to it). You can simply create the mnemonic and store those 12 or 24 words on a piece of paper calling it "paper wallet". Then each time you use a key you simply send the change to a new address and don't use the old one again. If the old one received any bitcoin in the future you still have access to it because you have your seed to generate all child keys.

P.S. When sweeping/spending coins from paper wallet you should also do it offline.