I'll be kind of side stepping the subject a little big and will just discuss the idea of "passion".
Having passion in something that you do, I think, is absolutely crucial in this industry.
The passion you have within a niche, will motivate you through the tough times. It will keep you going even if you're reading some 30 page article, because you like it. You love it. You find it infinitely interesting that it doesn't seem like work to you any more. Once you have gained that knowledge, you are then able to monetize it. That, I think, is the secret and the most wonder aspect of this industry.
Taking something that you love, and monetizing it.
Just typing this is sending shivers down my spine.
Now for me, my passion doesn't actually lie in any specific niche, contrary to what is generally recommended. My passion lies in affiliate marketing. The whole idea of affiliate marketing motivates me and, and a result, it motivates me to be passionate about any niche I read about or consider doing. This is not saying that every niche I come across, I just into, no, no at all.
I still pick one that I think is best, and pour my energy into it. Be it: research, late nights reading article, goggling a billion keyword, just reading, finding, digging for every bit of information I can find on it. But in the end, most importantly, I love every moment of it.
This, I guess, is better defined as overall drive.
But once again, I love it all.