The last thing you want to happen is having to go buy an article cheaply to fill a hole on your calendar. You shouldn't let these holes happen, although they can. This is why it's so important to work ahead. Having a content calendar is something some people do in order to know what topics are most relevant at certain times of the year. This is a great idea, because if you realize you're stuck for something, you can redress older content and update it to make new posts based off of them.
I probably don't need to talk about finding your keywords and writing content around them, as that's a tired and old strategy that rarely works anymore except in the most niche areas. Really, it's all about just writing content, seeing what works, and writing more around those topics. That's what writing has always been about in the first place: understanding your audience and writing for them.
There is one way to keep your content fresh that is fairly easy, as well: curation posts. This is when you find great content around the web and write some commentary about it in a post. Of course, these posts can get outdated if that material is no longer around. However, when you're stuck for a post, these can be quite helpful. Just be sure that you link to major reputable websites that figure to be around for a long time. Also, don't focus on doing these compilation posts too often. You want to have plenty of fresh, original content in the pipeline.
So the real trick here is to not overdo anything. Really, you only need 300-500 word articles most of the time. Sure, if a topic is deserving of 1000 words or more, go for it. But more often than not, if an idea is worth that many words, it's very likely you could split that topic into two or even three articles. Then you just come at the topic from different angles, focusing on different elements of that topic. If you find that certain articles inter-relate to each other, you should always deep-link them to one another. Not only does this help your site architecture, but it also makes your information that much more valuable to your readers. Who doesn't want to keep visitors on their sites longer?
What I'm saying is that you don't have to publish a white paper every week. There are plenty of questions out there that need to be answer in every field. As I've written time and time again, your audience will always have questions, so it's your job to provide content that offers up answers. If you don't have the answers, then offer suggestions on how best to proceed. People like to see that other people are thinking the same things they are. Making those sorts of connections is the way to truly create great content, not just maintaining well-oiled content machines. Focus on the human need, not scientifically or methodically, but organically. Your audience and future fans will thank you for it.
Photo credit: Flickr User Sean MacEntee, via Creative Commons License v2.0