What's the easiest way for my father in law to store 3 separate bitcoins (1 each for his grandchildren). He is planning 10 – 20 years at least of holding. If he were to get 3 separate ledgers would they last 20 years in a safety deposit box? Is there some way to just hold the seed on a piece of metal in the safety deposit box.
I'm going to be helping him. I own a ledger so I'm familiar with that but I'm not sure how long term that is.