Statistically, you could find a block in the first 30 seconds, then again it might not happen till after the end of the universe. And it will get to the point where a single cube is not capable of generating enough in a pool to pay for the power used to run it. Doubling down doubles the return for double the cost. So, there is a perverse logic in going for broke.

So, question, how long will it take a single cube to generate 25 bitcoins? (the only valid answer is twice as long as half of it)