Surprise or not surprise

Should trilogies be intricately linked so that they formed a continuous story, one that couldn't be properly told in one or 2 volumes or should they be so different that they each become a vehicle for different expressions of a single theme.

And haha of course, they could always be cheap excuses to milk the stupid and fat cash cows out there.

Hmmm... why is my blog being spammed. Its not if i update it so often...