better to set it at 4% average 7 seems to big seeing the current trend on the market
with 0.1 profit per day and 14.7 btc price in total you will need 147 days to roi if electricity is zero and diff remain the same, but you probably payed much less than that, you bought them from second hand right?
It really has been a great summer on difficulty 4 is more likely. And a lot of weeks we have been under it, which is nice.
Personally I like the bitwisdom calculator:
https://bitcoinwisdom.com/bitcoin/calculatorSo nice picking day, week, month. I like seeing it this way but I guess it's personal preference.