The most common question I get from new website owners, where the website contains a blog, is "how long should each blog be?" It's a question that there isn't actually a definative answer for, primarily because each website and audience wants something different - and if an audience is as wide, varied and awesome as the SEOAndy audience then they want a mix of long and short posts. Anything from 5000 words to 250 words could be right, only experience will show you.
This said there are some good bits of research which show what the average "ideal length" would be for various types of post (blog and social). One of the best bits of research I've seen was completed by two great socila tools Buffer and SumAll - it can be seen in the infographic below.