Mohsene, fantastic breakdown of the math here. I have both ETH and XMR contracts with these guys and I came to the same realizations you did, but I still believe in the contracts for this reason: dollar cost averaging. You could have straight up bought the coins and held them. And you may have done it at a high and 2 years later it's on a huge dip. Right now you get a little coin every day without the volatility of price. And you can swap to another coin for payouts. I have my XMR pay in LTC because I think LTC has more upside at this time, I may move it around again in a few days. So I agree that if you just do nothing for 2 years you may lose money, but if you keep an eye on your payouts and take advantage of times your mined coin increases in value (perhaps to up your hashes) then you could still make bank. The real trick is to combine that with someone that will consistently do that with you so you both can reciprocate referrals. Thanks again for the great post!