You stick with open source wallets; problem "solved". Obviously having to dig up old software and potentially having to make modifications to extract what you

You stick with open source wallets; problem "solved". Obviously having to dig up old software and potentially having to make modifications to extract what you need from them is not ideal, but at least it's possible. That said, the lowest common denominator methods of storing coins long term are pretty stable. They're just paper/metal/stone tablets/flesh with a 256-bit key encoded on them. Hard for that encoding to age any worse than, say, floppy disks which you can _still_ buy drives for today.