Yes the best is to update old articles at least twice per week because it enables you to rank higher even without backlinks.How often do you go back and update old articles that have lost rankings or traffic? Have you seen noticeable ranking improvements just from refreshing content without adding new backlinks?
That being said, not all keywords will require updates at all times. In this regard, I would only update keywords which are undergoing changes, whereas other keywords which are not undergoing changes do not necessarily have to be update.It depend on target keyword when writing the content to post, some keyword and content does not get much changes and features to edit for trending in serp,making of editable niche keyword content post are options in some niches expose.