Agree about paper wallets or some digital version of it, i.e. some encrypted file containing all your private keys. In general - for long term, store rather keys than wallet files. This way you won't be vulnerable to future versions of your wallet software being backwards incompatible or totally nonexistent in a few years.
Maybe this is what Danny Hamilton meant in post 2? I hadn't considered this but I'm now reinterpreting his post.
How do I get the keys from electrum?