I'm not sure I like the PPLNS method so much, as far as I can see from mineco.in. They estimate your reward by counting your contributions to the last 750,000 shares. With making the window so long, I'm not sure if this pool has much incentive for people to keep mining continuously. Although, currently its total hashing power is about 80 GH/s, which exceeds EMC's. I wonder if they can keep this consistently. And I did hear they had some long blocks recently.
There's no such thing as "incentive for people to keep mining continuously". Either the reward system is hopping-proof or it's not. If it is then anyone can mine whenever they want and get on average the exact fair reward for their contribution. If implemented correctly, PPLNS is hopping-proof. All currently existing PPLNS pools that I know of use a naive implementation that is only approximately hopping-proof, but still good enough.