I realised nobody appears to have any concerns about the temperature. Is 84 degree celsius a very normal working temperature for the chips? What will be their projected lifespan? Please correct me as I am currently still running on S7s. Bitmain's S7 28nm chips are already failing after long usage at ~60. Although the straight forward profit calculation shows a fast turnaround for ROI. But in the long run, will the repair fees start to close up the gap and S9 will still remain as the more profitable miner.
I've run some S7s with low fan speeds with temps at ~84-85c for extended periods of time as well and they worked for a good year before I sold them. Repair fees could get pretty costly as they might ask for shipment back to China on your own dime just like Bitmain. Replacing the fans with a higher-CFM fan could also work. Just a disadvantage of a high-powered unit, gets more and more difficult to cool em.