Yes, but in the next 2 months, you’ll likely make more money than in the previous 8. Use the earnings estimator for reference. And of course we are currently at a bit of a peak in costs. Chances are there will be some drops again as well. As long as you have at least 4TB to share, you’ll very likely get paid in less than a year, but almost certainly more than half a year (unless you use zkSync).
It’s more stable in the sense that it smooths out outliers. But if there is sustained dip in transactions, it will definitely still go down. There are also future changes planned for ETH that will substantially lower the costs. Additionally any one of them could switch to zkSync at any time. Bottom line is they need to still reserve those payouts.