It's no doubt been covered before, but I was getting a little frustrated with my edits to a page not clearing the cache until the next cache timeout, so I setup a trigger to clear the individual pages cache when it's been updated, which works a treat.
Essentially I have a trigger that has:
events:
Asset Attributes Changed
Asset Updated
Status Changed
Conditions
page (or descendant types)
Actions
Clear Matrix Cache
Include Current Asset? Yes
Selected Assets No asset selected
Anyways, just thought I'd mention it in case there's others out there who hadn't run across it.
Cheers
Dale
Or, if you're using workflow, its more efficient to trigger off the status change back to Live. 
Your trigger (while effective), would trigger way too often I suspect.