When you think about 'reinvesting' with bitcoin mining you should calculate carefully that the yield after reinvesting will actually be more than the yield you were getting initially.
Because of the difficulty changes.
Just to be absolutely sure your principal stake is not actually slowly shrinking.
This gets confusing, at least for me.
Just pointing something out to you. Might be important.
Oh, hey, i make big mathematical errors sometimes, so try to double check anything i say before you act on any of it.
My understanding is that the date at which you invest is irrelevant, as the price drops in proportion to the increase in difficulty.
E.g. - 20% increase in difficulty, 20% decrease in price.
Due to this direct proportionality, i'm not certain that your ROI(%) should ever change? Except with a change in block payout?