Another thing to remember is if Jordan didn't care about his series, and was only in it for the money, he could have easily published one or two books a year. The fact that he was taking up to three years to write each book, and the level of in-depth description in each books, suggests that he wasn't lacking in effort.

I'd also like to mention that I didn't discover this series until well after the 10th book was written. Though the series does slow down in the later books, the flow and quality of these books is pretty consistent. I only found Path of Daggers, and Crossroads of Twilight to be cumbersome to read.