Hey
displayChanged was called when the program uses another screen/monitor, it has nothing to do with dispose. As far as I know, you can use the same VBOs when you move to another monitor.
Moreover, I find you should read
this. You should delete VBOs when you don't need them anymore. You don't have to delete your VBOs at the end of the program as they will be deleted during the JVM shutdown. Releasing the resource is useful mostly when you don't want to lack of native memory at runtime.