If you want to save for long term, make use of either hardware wallet, paper wallet or at least desktop wallets. They are safer rather than leaving your cash on exchange wallets. Also, if you are going to be using a desktop wallet, you will need to always keep your desktop safe or you can just save your seed or private key somewhere very safe, copy out your public address and uninstall the software if you know your system may be prone to malwares. With the public address, you can always push in funds from anywhere and access it with you seed anytime you need to withdraw. However, you need to be extracareful with both your seed or private key cause if it falls into the wrong hands, your funds are gone for life.

Keeping your coins backed up does not necessarily mean you cannot get hacked. Backing up is a way to have access back into your wallet just in case you misplace or forgot your access details. If you do not maintain proper security of your assets, even with your back up, you can still get hacked.
Even your back up alone (your seeds) if thrown anywhere or someone ends up having an access to it is enough for that person to have access to all your funds. So extra security is always needed when keeping your assets.