The way I understand, they've been burned before by leaking all at the same time - there's an initial "shock", theneveryone forgets about it. If your purpose is generating the maximum amount of outrage and controversy (and, consequentially, change), it makes sense to publish things slowly.
Although I agree that the timing was probably connected with the US elections. But again, that's a good think - the only way organisations will change is if it will hurt them. Now both US parties know that they can easily be targets next time.
So is Wikileaks an organization interested in free information, or using "free information" for maximum political effect? If they are twisting the knife and trying to find out how to cause the maximum possible damage for one side only, then they are clearly not a neutral organization and obviously should be treated as such. If their goal is maximum political discourse, then they are obviously a political organization, not an information or "truth" organization.
Why do you think they wouldn't be causing damage for the other side, if they could? I mean, even if they had emails of the GOP, I doubt it would really hurt Trump in any way, it's not like he had their support anyways... Actually, it would probably help him!