Ali_R, since you are starting on Nitrix, 2x4 and 3x3 is a safe bet. Start out low and take Nitrix on the days that you work out would be my opinion. Unless you work out all week, it will generally be the days when you work out, although different opinions vary, you could take it everyday and supplement it with considerable amount of protein shake. Follow the directions, you will be fine.
On the subject of taking Nitrix for a month, yes, generally, it is true in some cases. But it depends on what bottle you are taking. A bottle of 180 is roughly for a month. I had written above that I had started just a few weeks prior on a 402-tab bottle. It is always advisable to discontinue such things and not be attached to it on a long-term basis, your body gets used to it and you don't see satisfactory results.
FrozenFire, good information as always.