The common advice is to keep all your systems up-to-date. This helps you get new features and security fixes. This is pretty good advice for your operating system and web browser. But one exception I apply to this rule is phone applications.
There are multiple reasons you might want to avoid updating your applications.
As long as there’s a large portion of users that are on an old version of an app, the developers won’t be able to break or get rid of their APIs. Since they will still want to add functionality and do fixes for their new versions, they will have to grow their API in a structured way and keep it stable for a longer time. This will benefit you if you ever want to implement the same API to make a compatible server or client.
Newer != Better
When you update your system packages, you usually get stability fixes and new features. This is hardly the case with most apps. If you are happy with an app, an update will probably mess up your workflow and change things for the worse.