Paper wallets can suffice, but it entirely depends on your threat model. If you're concerned about them getting damaged or destroyed via fire, water or anything that could potentially come in contact with them, a metal wallet tends to have higher security based on that. However, the major concern would probably be physical security such as theft. If it's safe from theft, then the other outcomes are relatively low.

However, this depends on your current arrangement, and whether you're storing them in a house that's prone to flooding or has old questionable electrics. Only you can really determine that, otherwise you risk compromising your security. If you're storing your paper wallets outside of your house, then look at the environment you're storing them in, and decide from there.