If you’re a long term believer in crypto, the answer’s obvious to me, and that is to continue mining with the cards even after they have broken even. Power’s not an issue as you stated, so there really isn’t a point where it might be more profitable to buy coins than mine at a loss, but if you truly believe in Ether, keep mining it! There’s no guarantee the price of ETH will go up, but if your viewpoint is that crypto will become more successful in the future, go with it.