Are you considering that the maintenance fee will be increasing in a few days?   Until 4/20 the fee is based on $0.06/kwh electricity.   The price will go back to the normal $0.075/kwh electricity.    That means the maintenance fee will probably be around $0.109375 / TH / day.   The S15 will still be profitable at the current BTC prices, but the amount of time to ROI will be impacted.

Full disclaimer:   I sold my S15 hashes yesterday.   I only had around 145 TH, but still it wasn't easy to sell out as the market is still pretty thin.   I'm expecting to be able to buy back in next week under 0.006 TH/BTC next week.  I could be wrong, I often seen pricing that defies what I expect.  However typically the price of hashes tends to be around what gives 180 days ROI at the current difficultly.    (Currently the pricing seems to be higher than 180 day ROI)

Now that there are more choices for sha-256 mining, we may see more modest difficulty growth.  However if the price of BTC climbs one would expect the difficulty to climb.  

Personally I have a mixed history with cloud based mining.   I've done extremely well at times and I've lost my shirt other times.    If people are mostly successful at HASHNEST it would be great to hear how you do it.  

For the record every time I've played just growing my hash rate game, I've lost big.   Strangely the best I every did HASHNEST is when I just gave up and decided it wasn't even worth my trouble to sell.   I didn't log in for months, maybe a year and when I did I had actually mined a full bitcoin.   So maybe not worrying about selling is smarter than trying to avoid a possible quick price drop that I'm expecting.   However over the long term I always expect the price of hashing to generally decline.