It's not about rising difficulty, it's the question of, if the difficulty were 1 billion today, would the device earn money above its electricity costs. The answer is yes, about $17.50 a day:
Even that depends drastically on your electricity costs which vary from < $.08/kw to $.22/kw. In Europe, power is even more expensive. Obviously if you have free power, then that's a different story - once the purchase costs are paid for, then you never shut it off.
free power for me (running it at my office!)
I wonder, after the first 6 months if we couldn't bring the devices home and set up a mining arrangement with some local business-office that has a spare room and set electricity costs... could extend the profitable life of the device another year or so.
