I agree, the calculators are BS. As I write this the next estimated difficulty increase is < 9% not the 20% everybody thinks will continue forever.
bitcoinwisdom.com/bitcoin/difficulty
It will not continue forever, but it continues for a very long time:
http://mining-profit.com/bitcoin-difficulty-historyAnd why should it stop? What you think? Major miners still have cheap electricity and a lot of new mining hardware
take the best machine power wise on the market an sp10 in low power mode does 1th at 700 watts no machine is better then .7 watts a gh. you to need spend 3k if you are lucky to get one. I did 10 cents a k watt that is cheap . no cooling cost (not realistic) 421 a btc .
so the most efficient machine know to man needs a 9% diff rate to make a few bucks if you get 10 cents a k watt and cool for free.
This translates to some slow growth. Or big price cuts in gear .
at 20% a loser
at 15 % a loser