However, after a set amount of time, if you have not used any Java applets, then the plug-in will be disabled again.

Java is configured using the Java applet in the Control Panel. It has an Update tab with a checkbox for automatically checking for updates. Un-checking it, doesn’t seem to do anything.

Applets need to be cached to become instantly available after they are installed. Additionally, applet archives should be compressed to reduce the size of the download.

If you still need Java 6 for Web applets after installing Apple's latest updates, there is a way to restore it and override Apple's preference for the use of Oracle's Java 7.