There’s not a rule per se as to how much content needs to be updated, but you can use your common sense.
If all you change is a few words or a date, or just add a picture for example, you aren’t really changing the content.
People like to try to game this system by moving paragraphs around but not really changing the point of an article, for example. Google is wise to this and will not reward you for it.
However, if you have an article like “5 Predictions for SEO in 2018” and you update it to be “5 Predictions for SEO in 2019” and actually change most of the content, there are ways to help Google find out about it more quickly.
But before I share that, I want to be clear: the content needs to be different.
You can’t just post the same five predictions you made in 2018 and put them in a different order.
You can’t use four of the same five and just change one.
That’s not going to fly.
I use a real-world test. If I sent this article via email to my loyal followers, would they find value in it, or would I be irritating them by sending the same thing I previously sent?
Google is likely to react similarly. – Read more