Some people look at the 5 year contract from PBMining and are turned off by it. I don't see why though. You make
Besides, the vast majority of your return will come in the first year. And unless the BTC exchange rate increases dramatically, you might not want to even bother collecting the the last few satoshis that you will collect in the last couple of years of the contract, lol.
So just think of it as a one year contract when you do your computations. It's still a pretty good deal.