Considering where the difficulty will go we're looking at 1 year to ROI.
Yes, if you were starting from scratch the ROI would probably be a year or more but everyone's situation is different. My current hardware paid for itself in July so if I sell my 20 S5s for something like $300 each I would have $6000 towards 5 S7s. That would make my initial investment about $3500 with 24,300 GH/s, 6050 Watts, and power at 0.10. If you plug those numbers in it shows 94 days to break even. Even if difficulty made a huge jump in the next 3 months it would look like maybe 188 days to break even for me. Like I said, everyone's situation is different.
Now that you save on electric you can run double the hashing power with the S7 as you could before and you will do it. If everybody does the same thing as you it will cause a major global hash rate speed the BTC price will drop DIFF will go through the roof and the market will crash and all your S7 will be worth nothing. anyway that's life. but the price of the S7 is ridiculous. Look at the global hash rate since the S5+ came out it went from 380 PH/s to 416 PH/s. Now how much higher you think its going to go until there is a big CRAAAAAAAAAAASSSSSSSSSSSSSSSSHHHHHHHHH !
WELL GREED CONTROLS THE MARKET THATS LIFE. BITMAIN SHOULD KNOW WITH THAT PRICE FOR THE S7.
If everyone did like clgrissom3 we would have another bull run and we would all be swimming around in gold paint and drying it off with dollar bills.