May I know which GreenHopper version are you using?
Anyway in the latest GreenHopper version, you should be able to enable the "Parallel Sprint", which basically allows you to start multiple Sprint at a time. Kindly refer to the following documentation for more info on this:
I hope that this will help!
Scaling an agile organization and setting it up for success over the long term is a hard thing to do. We hear a common set of questions from customers all the time, questions like: Can agile scal...
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