So I have a Coinbase account and from all their free crypto promotions I have around $150 of Eth. I'd like to start adding some more to this to hold very long-term - is there a certain exchange or some other way you'd recommend, like Kraken or a hardware wallet?
Sure. If you have a serious amount of savings, the best approach to balance security and practicality is to protect your coins using multisignature, or multisig. https://en.bitcoin.it/wiki/Multisignature