If you are using Jira Server and you change the license count, you will have to get a new license for your plugins. If you stay at the same license user count, I don't think you have to renew the plugins at the same time, they should remain at the same renewal date.
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events