I will write articles however long or short you need them to get your message across. By way of advice, I would suggest anything less that 500 words don't really cut it. In fact, you should really consider producing articles over 1000 words in order to bring value to the reader. Articles of value to the reader should, for example, deliver a breakdown of a given process to help the reader implement a strategy or perform carry out a task. Always be teaching. Always be willing to give away what you know for free.