Various notes on /usr unification

I believe /var/tmp is generally considered to be "stable across reboots", so at least that much would remain consistent. *Old* files may be deleted from /var/tmp, of course, but while files in /tmp are only valid for the life of a single process (and thus can always be deleted after a reboot), files in /var/tmp represent transient data which may nonetheless remain useful well after the process which created it has exited.

Since /var/tmp is defined as stable it's unlikely to be located on a RAM disk, but applications using large temporary files must still be prepared for the possibility of running out of free space.