I planned to take a break after I finished writing my first serial (basically a really, really long novel), maybe work on something else. But I missed the story too much. So almost immediately I started working on the (already planned) sequel. And as soon as that was finished, I worked on the third. As soon as it's done, I'll start work on the next.
I just can't "take a break" from writing unless it's short or I'm busy doing something else. Especially with a series story, I love it so much and want to know what happens next!! There's never any "brain exhaustion" for me--some sort of exhaustion, maybe, but not to the point that I don't wish to write for a long time. Plus, to take too much time away from writing can lull one into the habit of NOT writing regularly, which can become dangerous. Even if you aren't working on the next novel (if you have plans for another one), you should perhaps try working on something else writing related, just to make sure your writing muscles don't get out of shape.
You say you're posting progress entries in a blog, so at least that's some sort of writing. It's better than nothing. And a break is just fine--I know I need them at times. But I'd really try not to stay away from fiction too long. Perhaps the exhaustion will resolve itself a lot quicker than you think? (I thought for sure I'd be sick and tired of my story once it was finished, but nope, a day or so later I was working on the next!)
