When to clean up /var/tmp?

/var/tmp is not defined in POSIX, but is defined in FHS : 5.15. /var/tmp : Temporary files preserved between system reboots 5.15.1. Purpose The /var/tmp directory is made available for programs that require temporary files or directories that are preserved between system reboots. Therefore, data stored in /var/tmp is more persistent than data in /tmp. Files and directories located in /var/tmp must not be deleted when the system is booted. Although data stored in /var/tmp is typically deleted in a site-specific manner, it is recommended that deletions occur at a less frequent interval than /tmp. This is a very difficult definition for real life situations. A package does not use /tmp, because the files should not be deleted on reboot for some reason. If a package fails to cleanup its remains in /tmp the distribution/admin can safely clean at reboot. When and how should we clean up /var/tmp? What can packages and software developers expect from /var/tmp? Do we have to clean /var/tmp after n reboots? (see also https://unix.stackexchange.com/questions/86297/what-can-go-wrong-if-var-tmp-is-on-a-temporary-filesystem and https://unix.stackexchange.com/questions/30489/what-is-the-difference-between-tmp-and-var-tmp)