Greenhopper Assignee population in Task Board performance is bad

Using the Task Board in the Agile view, the "All Assignees" dropdown is slow (couple of seconds) to populate the list. Staying in the same view, a second request for the dropdown is quick. If the project is changed and the same dropdown link clicked, it is again slow to populate.
This suggests the lack of a backend system cache of the Assignees for Greenhopper use.
The official documentation https://confluence.atlassian.com/display/GH/Using+Planning+Board+Modes#UsingPlanningBoardModes-Assignee provides an unhelpful suggested approach.