>   I guess it would be possible with a schema processor like 
> Saxon to load once the schema and loop over the 30,000 files 
> with a little custom application.

Yes indeed. Something like this:

<xsl:import-schema namespace="abc" schema-location="abc.xsd"/>

<xsl:template name="start">
  <out>Validated <xsl:value-of
select="count(collection('source-dir?validate=strict;on-error=warning'))"/>
documents</out>
</xsl:template>

Michael Kay
http://www.saxonica.com/