I keep a lot of my alts on exchange. Not the best practice, but it is what it is. If you host them on mulitple exchanges you don't have a single point of failure. Any huge bags I have I'll download the wallet for the coin itself and install on my computer. There's also paper wallets if you're holding long term. I've heard a lot of people using jaxx.io but recently read something about a vulnerability https://cointelegraph.com/news/jaxx-wallet-vulnerability-users-report-400k-funds-thefts