I advice caution. Earnings go down each day and I don’t think people know when to stop adding. Also, when Ethereum switches to Proof of Stake its going to have a huge negative impact on all mineable coins.
There is no way I would build a big farm now unless I got Chinese electricity prices.
Something else to keep in mind, never confuse Mining with Investing. Don’t think that mining is more profitable if you hold your coins and the price goes up. Once the coins are mined, the value is earned. If you decide to keep that value in crypto form it is an investment and should be calculated independently.