The Atlassian Community Forums are currently in read-only mode. We will be relaunching on a new platform on September 22 (read more here). We apologize for the extended downtime. For concerns or questions, please email communitymanagers@atlassian.com. See you on the other side, on the new Atlassian Community Forums! :)
Advanced Roadmaps has a limit of 5000 issues in a single plan, so if you exceed that it is recommended to spread the work across multiple plans. Please have a look at this KB for more information.