Give every article an owner and a date
Each article needs one person responsible for it and a last-reviewed date. Without an owner, nobody notices when a button is renamed. Without a date, you cannot tell what has been checked and what has not.
Tie updates to product changes
The cheapest time to update an article is when the product changes. Add a line to your release checklist: which help articles mention this feature? Edit them the same day the change ships.
Review the articles people actually read
Do not try to check everything every month. Sort articles by views and by how often tickets mention them, and read the top ten. A wrong article that gets traffic costs far more than a wrong one nobody opens.
Use tickets as the signal
When a customer writes in after reading an article, the article failed. Tag those tickets with the article link. A few tags on the same article tell you what to rewrite first.
Retire what you cannot keep right
Delete or merge articles about retired features, and redirect them to the nearest current page. Fewer, correct articles beat many uncertain ones. Keep a short list of what you removed in case a customer asks.
Close the loop with search
Look at the searches that return nothing. Each one is a question customers expected you to answer. Write the top few as new articles, using the same template every time.