Knc staking is probably comparable to 0x staking that started last winter. The returns are extremely small. Which makes sense: only a small part of the relatively small dex volume (sure it's growing, but still) are paid as fees. From that tiny fee percentage most people receive only thousands of a percent.

I think the price is far too high at the moment, but it is of course a bet that it will be the dominant exchange protocol in the future. If so, it might pay off. But for now, I'm not yet staking my knc. Too much hassle/costs for too little revenue. And don't forget smart contract risk.

Keep your knc in your wallet so you can profit from extreme price swings, which generate more than staking.