Not to insult a free power guy like mikeywith but he will always prefer cheaply priced mining gear over new.
You are 100% correct on this one, we all have different ways to run our businesses and to each their own goals, mine has always been on the low-risk side, in other words, I always focus on fast ROI, and the only time I did something different I was screwed.
Telling people that I have 300KW to use and they all are S9 seems stupid, some would suggest that since my power is limited but free I should go for more efficient gears.
In order for me not to push things too much, I usually keep the load around 200ish KW, with just about 180 S9s in that farm, what I can alternatively do is use that 200KW for S19 pros for an example, and then I will have about 70 of them that hash at 7700TH instead of just 2500TH, I am sure many people would have gone with S19 pros or T17 at least, but my maths won't work that way, and here is why:
S9i 14th costs about 60$ shipped
S19 pro costs about $3500 shipped
This is $10,800 vs 245,000, in fact, even if I were to go with T17s, the maths will still favour the S9s in every single way.
Also, it isn't just the ROI factor, it is the robustness of these gears, in my other mini-farm since power is pretty limited to about 180amps, I can only use about 28 S9s, which is a bit less than 390TH and isn't worth the trouble, so I went ahead and filled with more efficient gears (a mixture of the 17 series) and now I have a ton of dead boards and PSUs, after having re-done the math, I would have been better of with keeping just S9s in there, but well, a lesson learned.
I plan to close down this mini-farm by next year and expand the other one, I would like to get a 600Kva transformer (won't be easy but doable) and I will only place S9s in there, my initial plan was to get rid of those Antminer 17 series and replace them with MicroBT M21s, but two things got in my way
1- M21s price increased after the 14k bull run and the shutdown of bitmain shop.
2- People here are heavily focused on ROI as well, so nobody is willing to pay $1000 for an S17 pro that does 52th when they can buy about 15*S9s for the same price and mine at 200TH, so I am stuck with these 17 series gears and looks like I am going to milk them until they die on me.