It is funny that people are quick to complain when there is a string of bad luck but I have never heard anything when we get good luck. I can understand your confusion if you don't completely understand what the variable are in Bitcoin mining but I think it should be easy enough to understand what an estimate is.
Mining variance means on average you should get a similar amount of payments that are above the expected value to those that are below that value. Why isn't that the case with this "service"? When have payouts been greater than expected? Also, name a bitcoin miner that will still be mining profitably a year from now, never mind 5 years.