It's impossible to stand still in IT. You're either moving forwards or backwards.
Networks are complex systems which have to do with almost constant change. The traffic generated by users is constantly evolving, hardware and software phase can impact at any moment, and hackers are an ever present problem.
To work as a professional in either the network or security field we will need to continue to develop our knowledge. Both fields are remarkable in the change they have experienced in recent years which shows no sign of abatement.
To become a highly valued professional, never stop learning!