The extendlet-check-period Element
From Documentation
[Default: -1 (never expired)]
It specifies the time, in seconds, to wait before checking whether a resource loaded by an extendlet is modified. An extendlet is a processor to load the resources usually located in classpath, such as ~./zul/desktop.dsp.
Resources located in classpath are usually packed as a JAR file, so they are immutable and not need to check if modified. However, in a development environment, you might want to check if they are deployed without reloading the JAR files.