IMHO, it's not worth it.

You need to include the difficulty increases in your calculations. Your 8 months could easily stretch into 20 with the current rate of difficulty increases. Most people are making the assumption that BTC will increase in price with difficulty, but so far the price has remained the same.

The only way I see mining being profitable in the long run is having low/no electricity costs and/or BTC value to increase. alot.