Even though I try to be diligent about keeping my dependencies up-to-date, they tended to always drift away from truth -- updating is a sometimes frightening chore that's easy to put off.
I'm enabling Greenkeeper.io on all my OSS projects, and it makes this chore much easier.
The old adage goes: you can only fix what you can measure. In the same sense, Greenkeeper measures the churn in your dependencies, and allows you to manage (fix) the requirement for change that comes with it.