Why would I trust Coinbase more than a bank´s safe? What I would do is divide the key in two or three parts and store each on a safe in different banks. For small amounts, just leave it to two people you trust or, for safety, leave copies to four people.
Agree, I opened my Safety Deposit Box (SDB) for only $30.00 ($15.00 for advance key + $15.00 advance rental). Rental of $15.00 a year and you just need to maintain $10,000.00 Average Daily Balance (ADB) in your passbook, ATM account, current account, or any account you have in your bank. We need to be secured, because we do not know what tomorrow may bring.