All Netbeans modules should behave responsibly with regard to performance. They must not affect startup time negatively, they must not increase memory footprint significantly and they must be responsive at all times.
- startup -module initialization should be as lazy as possible, not to increase startup time
- memory footprint -heap space allocated by module's data structures should be freed as soon as not needed, excessive caching of data is not good
- UI responsiveness - module's actions, menus and windows should satisfy the UI responsiveness guidelines as stated in What is UI responsiveness document
Source: NetBeans User FAQ