Electrum is the wallet that you should consider. It's the safest wallet for storing your Bitcoin for long-term. But, you may go with Electrum as cold wallet. A cold wallet is much safe for long-term storing of your Bitcoin than a hot wallet.

Some people believe that you should never connect to internet even for a once on the system where you store your cold wallet. While others believe that you may connect to internet during wallet creation and once it's created then you should disconnect it forever from internet to have facilities of cold wallet.

With the help of electrum you can do both of those but I prefer you to go with offline one as that's a little bit more safe for you. Here's a guide that you read in order to create an electrum offline wallet. The software based cold wallet would be more than enough to safely store your Bitcoin for long term.