Trust me... this one I know from experience that it is the hardest one to do. There are so many things to do while running a company that putting out good social, or blog content in a timely fashion is really tough to accomplish! Seriously though... we have talked about creating a membership area to your site or having the SEO benefits of fresh content on your site a few times... this is crucial to keep viewers eyeballs on your business and to help stay on Page 1 of a SERP. (Search Engine Results Page)
If you are pushing social then you are likely creating a social calendar... try to time your blog posts in time with your social media to theme out your content. It also makes it a little easier for ideas on good content.
If you have your social out ahead of time and scheduled, you can schedule your blog posts out to align with your social posts too! This will give you time to review your posts and will still allow you to be able to handle all of those fires that pop up without sacrificing the fresh content.
Now... The interval at which you post is up to you and what you think works best for your particular business. It could be weekly, monthly, quarterly etc. You get where I am going with this. The most important part is to be consistent. Your viewers will begin to expect it and even better... look forward to it!
Also, one thing that I have gone for with both social and blogging... (as you can tell) is to keep it short and sweet! Snackable information if you will. Like most people, we are all busy and very few of us have enough time to read all that we need to. So pick small items or breakdown big ones and give out the info in chunks. It keeps you rolling and your viewers interested!