My RSS does not update.

I created (I thought) a feed that reads my database and creates an XML document. I then linked the XML document to my browser, which displays the contents fine and appears to work just like any other RSS feed. Except, when the database changes, and the XML document is updated, my browser RSS dropdown does not update. This happens in both IE and Firefox. Any ideas?

<cfquery name="getAdvancedCf" datasource="mySource">
SELECT * 
FROM announcements_rss
WHERE ID=91
</cfquery>


<!--- Map the orders column names to the feed query column names. --->
<cfset columnMapStruct = StructNew()>
<cfset columnMapStruct.publisheddate = "ANNOUNCE_DATE"> 
<cfset columnMapStruct.content = "DETAILS"> 
<cfset columnMapStruct.title = "SUBJECT"> 
<cfset columnMapStruct.rsslink = "URL">

<!--- Set the feed metadata. --->
<cfset meta.title = "My Title">
<cfset meta.link = "http://feedlink">
<cfset meta.description = "Orders at the art gallery"> 
<cfset meta.version = "rss_2.0">

<!--- Create the feed. --->
<cffeed action="create" 
    query="#getAdvancedCf#" 
    properties="#meta#"
    columnMap="#columnMapStruct#" 
    xmlvar="rssXML"
    outputFile = "feed.xml"
    overwrite = "yes"
>

<cfdump var="#XMLParse(rssXML)#">