Out of juice?

I really hate this new trend of the people behind the series, deciding that it's a good time to start reviewing the past of the characters when they are out of juice to give us something new.

I gave up on Lost because of this, now it's Jericho doing the same stuff (at least it only lasted half an episode), but what really pisses me of is Heroes, next episode is going to be a flashback on a lot of things, at least, I hope it's revealing.

So are all the writers out of juice or just on a temporary writers block?