If you plan to sell or exchange your coins over the next few years, experience shows that storing coins in a cryptocurrency exchange account is no different from storing them in a wallet. And in many ways it's even more convenient.
You didn't get the point, the reason why you shouldn't leave your coins in exchanges because you can't know the exchanges is still operated or not in the future. If you have leave your coins on an exchanges which never got hacked until now, you're lucky since every year there's always an hack incident. I would rather spend some satoshis and times to secured my coins fully 100% on my wallet rather than leave them on exchanges to save some fees.