How to verify if a private key works without exposing it to the internet.

Yes I’m old school and for more than five years now I’ve been piling up BTCs on a dozen of paper wallets securely created many years ago and they have never touched the internet. All I do is to keep them hidden on two different places (actually two different countries) and use the public keys to send BTC to them. The day I decide to spend my coins I’ll for sure buy a hardware wallet and sweep the paper wallets. But for now I’m trying to figure out a way to verify if these private keys really work without exposing them to the internet. I guess it’s impossible and I’ll have to just trust it until I decide to sweep the keys, right? Or anyone can think of something else? Thank you.