Typically, I go back through older pages on a schedule of every 3 to 6 months, particularly if the page’s performance begins to decrease. If done correctly, a nice refresh can absolutely help get those rankings back without adding any links.
Yes the best is to update old articles at least twice per week because it enables you to rank higher even without 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.