Yes you should never delete a wallet. Satoshi says so. Maybe coins are sent there accidentally and be you don't have access anymore? Or if there is an airdrop or something.
Also usng blockchain.info is fine. I wouldn't store my life savings in it though. I use it as a spending wallet. For my main savings wallet I use none other than electrum, best wallet ever made.
Using online wallet never is recommended, to use it only if you need it. The only one online wallet i trust is Coinbase, but it still is not 100%.
I also recommend Electrum as good desktop wallet. Another good and very user friendly desktop wallet is Exodus.