If you really want to look at the long term, think of it this way. Eventually, an equilibrium will be reached between the people who can't maintain profitability and back out, or people discouraged with the btc values and back out, and those who stay in. Difficulty will level off, and eventually profitability will return with you at an advantage. This is in the long hall. Bitcoin has had one boom so far and I don't believe this is the end for it. I'm at about 1ghash/s and I'm satisfied to hold it out.