Keeping a website up-to-date employs several factors to maintain site health, security and speeds. Areas to update are versions of PHP, site themes, content management systems (CMS) and the various plugins which have been added to the site.
Before actioning any available updates, it’s very important to make sure said updates won’t cause issues. Some PHP updates can cause critical errors resulting in the website being completely down. Plugins which haven’t been updated for a long time can deliver the same result, too. As you can see, blindly guessing if an update will work is a complete gamble. Developers use staging environments to test compatibility before deploying the updates to the live site, thus eliminating risk.
As a website grows and incorporates more and more features, plugins and integrations, there are far more updates of which will become available. Avoid mass-updating plugins and features as it is difficult to determine the issue should it go wrong.