This is a difficult question, because it differs from one writer to another. someone may wish to write a long story, others may wish to cut the story short. It depends on each writer as to how much information one wants to include in an article or post.
Long or short post/article
It is important that you take your readers into consideration. People have at least 14hrs to spend. They wake up at 06h00 some go to sleep at 22h00. They must go to work, return home to do certain things.
Spending time at work which at most is 8 hrs, rush home to do home chores, relax and watch days news on TV, or something else. Internet contains billion pages and articles. Therefore the internet user does not have all the time in reading everything that appears online, even first page articles.
So the internet user lends the internet writer a small portion of his/her time to the writer. What appears online will be read by user within time allocated to that particular activity.
Must you write a long or short post/article
I might not give a straight answer, but I wish to give you a practical scenario. People differ in life, there are those who wish to read details of your story, others are only interested in the main discussion. What you need to know is that people buy newspapers, magazines or books to read.
Guess what they do when reading a newspaper, the first page is important, important because there is/are eye catching headlines. So they read the first, second page and further look for something interesting. the rest of the newspaper pages are left unread.
You have a decision to make
If you write a post/article you must take into account the quantity of information available online, and the time the internet user is prepared to spend browsing that information. I have said before, the browser does not have all day to read, the amount of information available online is overwhelming. That serves as a guide as to the quantity of information you must include in your post or article.
Back to my question, “How many words must a post/page/article contain” In case I haven’t answer this question properly, well you may write 500 words posts/article & get huge traffic. Someone may do the same, but get poor responses.
What’s important here is the content. If 500 words article gets huge response, reasons may differ, the article is interesting, or it reflects online current trend. Or it may contain useful and interesting content internet users are searching for.
I need to advice you, internet users aren’t interested in the length of your content, but the usefulness &relevancy of information to their needs.
The moment you put pen on paper think about the readers/internet users. Does the subject interest them, most importantly, does it address their current problems. People go online to find solutions to their problems. Your tasks therefore is to tell them where/how to find solutions.