As I see it, there are two types of miners.
TYPE 1: Mines coins based not on what the coin is worth currently, but mines coins based on the change that coin may increase in value at a later time.
TYPE 2: Mines the most profitable coin at that time.
It sounds like you are a type 2 miner.
Based on that, I might consider beginning to sell off some cards and here's why
1. Nvidia will release new cards this year. I expect the next generation of Nvidia cards to be better at mining ETH than they are now. AMD is supreme in the ETH mining market, this is why I think Nvidia will seek to make improvements there. If you are going to continue to mine ETH, I might consider starting to sell some cards off now slowly. Get some liquid fiat to buy the next gen cards.
2. if you believe #1, then you should also think AMD cards will drop in value after the new Nvidia releases.
Your other option is to begin mining other coins. Most coins RIGHT NOW wont make you as much daily income as ETH. However, some of those coins may make you MORE than mining ETH - IF you mind and HODL.
If you can mine and HODL , there are many opportunities out there. I've always felt this is where the real mining profits are. However, if you must spend your mining profits monthly, this wont work for you.
Excellent analysis. I'd give you merits if i had some.
Just to add, selling off some GPUs now is truly a wise decision because it's value will surely decrease once a new generation of GPUs are released.