I admit I worry about this too, since on average it takes me about a week to write each of my posts (I have very limited free time). Which is why I would never blog about fast-paced events that will be yesterday's news by the time I finish writing. But given how quickly posts fade from the limelight, I don't think it does any harm to have multiple posts about a topic, so that people who didn't see the older posts are still aware of what's going on (but you don't want posts to contradict each other so make sure you've got your facts straight).

This is especially true for important things like Steemit updates or external news that could affect the platform or its future development direction. So I wouldn't worry about it too much. And if you know of some earlier articles that are relevant, or even discover some after the fact, don't hesitate to provide links to them in a "Further reading" section at the bottom of your post!