Here's a trick to improve the start up performance of JavaFX apps.
All you need to do is one line addition to your JNLP files.
The update element is used to indicate the preferences for how application updates should be handled by Java Web Start is not set right. The update element can contain the following optional attribute:
check attribute: The check attribute indicates the preference for when the JNLP Client should check for updates, and can have one of the three values:
option 3 will improve the JavaFX app startup time.