If Bitcoin is stored in a wallet that only the owner has the keys to, the coins are safe from all online attacks. The only thing that this platform can not deal with is the risks of the real world: the threat of theft, a bullet in the head, fire and floods, as well as the threats that come from the owners of purses themselves. The biggest reason for lost coins is not the third parties — it's ourselves. Stories about lost hardware wallets, rewritable hard drives and forgotten passwords do not need to be distributed. Stolen or weak passwords is the same problem like the lost keys to the wallets. Any private key solution must take into account the risk of human error. Otherwise, even the most bizarre hardware wallets and the strongest safes can turn out to be redundant. So it's all up to you.