I did several of the ******'s yesterday for my free nx, and I'd say for some it took as long as 30mins to complete. In the end what I was able to earn came to about 100 nx per minute. Most of the ******'s were pretty simple, though I will say keep your answers short, especially when it allows you to choose more then one. I did a drinking one yesterday with 29 different liquors, & I had to do a ****** on each one just to earn 2k nx.
The one I was going to do that they changed was the netflix purchase for nx. It was originally Netflix cost for 17.5k nx. Now is someting closer to netflix cost for about 8.5k nx.
Be careful with the offers dealing with your credit. My wife works in the fraud department of a credit card company, & she says stay as far way from those as you possibly can. If not you could find your information stolen, even from sites that are using Nexon to get clients/customers.