Trilogy Question

I'm interested in the trilogy trend. So many authors seem to be doing this lately, and I am conflicted about whether to read the books as they are published, or wait until the entire series is out.

With the Hunger Games for example, I waited to read the first two until a month or so before the last one was out. However, I read Divergent when it came out, and now I'm regretting that decision. How much of that story will be fresh in my mind when I read the next in the series this summer?

What do you do? Do you re-read before the next one? Do you wait? Or are you able to keep the details fresh, and simply read the books as they are published?