The maxUsingDuration parameter is used to set, in ms, how long the usingAction effect will last for when holding down the right mouse button. This is required whenever using the usingAction attribute. If it is not at least 1, usingAction will not have any effect.
maxUsingDuration = "5000";
Adding this line will allow you to hold down the right mouse button for 5 seconds before the usingAction needs to be retriggered.