I just thought of a $var addition to be able to get the duration before the time is unset with the .unset property.
I used the search feature and it turns out 2 other people suggested it, but I thought I'd contribute, to see what others think.
I think it'd be a good addition because, because most of my scripts need to know when they are being unset which brings me to my final idea which may look and sound stupid but maybe something like..
On *:VAR:Set: {
echo -a $1 was set.
}
On *:VAR:Unset: {
echo -a $1 has been unset.
}