It is like the true story of Frank Lucas the drug king pin who focused more on moving volume of heroin versus trying to get top dollar. Like you said, you can spend 10 hours on one article, but the value you put into it may not be reciprocated in the end.

In short, you need to create as much content as possible in the shortest amount of time. Is there a minimum standard? Sure, it cannot be sloppy and poorly written. However, your returns begin to diminish when you spend hours and hours researching for a blog post.

The only time that I will spend tons of time researching is when I am being paid to do so when writing an article for a client.