Utilizing older dependencies is typically acceptable, barring any potential security vulnerabilities.
The main issue arises when a need for a feature from a newer version arises, requiring updates. This process can become quite cumbersome, particularly if the differences between versions are significant.
Furthermore, there may be other dependencies reliant on the updated one, necessitating further updates.
Maintaining project updates is usually smoother (aided by unit tests). Therefore, it is important to consider the necessity of incorporating new features.