Offline Mode. The offline mode of securing bitcoins is called cold storage.Backup your entire bitcoin wallet early and often.
Software.Keep your software up to date.Encryption.Multi-Signature.The Bottom Line.
Cold storage is good as well, but your bitcoin is secure well if you use bitcoin wallet for it, until you here your bitcoin wallet password with anyone else,. bitcoin wallet is the best way of secure your bitcoin, you can have warm and cold both kind of storage but the best choose is only bitcoin wallet, market now have a lot of hardware and software wallets that we should use to secure our bitcoin for more than 5 or 6 years as reward of profit.