[xsl] Getting the length of a duration

Have I missed an obvious better way to write this function?

    <xsl:function name="xmltv2tgd:durationLength" as="xs:decimal">
        <xsl:param name="duration" as="xs:dayTimeDuration"/>
        <xsl:sequence select="days-from-duration($duration) * 86400
            + hours-from-duration($duration) * 3600
            + minutes-from-duration($duration) * 60
            + seconds-from-duration($duration)"/>
    </xsl:function>