How much (%) of your mining income (or profit) goes back into expanding/replacing mining capacity? I know mining is for people with money but I wonder what's the smallest investment that can actually be self-sustaining in mining?
Myself I have free hosting (paid in bulk by another business of mine). but even so, the total returns on my mining are not enough to get something more than an S7 after several months, an S9 at the moment would mean putting some of my own money into this..again. So I wonder how much I should set aside (10, 50%, 100%?) to replace old hardware like S4,S5.
Free hosting? I would suggest, and this is just me and what I do, without free hosting, is take the money I get from mining, move it to an exchange and trade in alt coins to make more Bitcoin, which I am getting really good at, and then use the coin to purchase another S9 when I can, rinse and repeat.
If you have free hosting then you have no electric to cover like I do so you should be able to get going in no time at all as at the current Bitcoin exchange rate an S9 costs about .41 Bitcoin.