The return on investment (ROI) date given on your site may be a little optimistic.  You have assumed there will always be 25 bitcoin per block, ignoring the halving mid next year to 12.5 Bitcoin per block. 

Your ROI breakeven, at $240 per Bitcoin, may be closer to 900 days rather than 615 days.

This halving is ignored by a number of the ROI calculators.  At least with the coinwarz calculator you can experiment with the number of Bitcoins per block.