We have the time limit setting in the ini set to 
45 seconds, but that doesn't have any effect.  I've
also tried explicitly setting the time limit, and it
also has no effect.  With or without the call to
set_time_limit, the script below will go for hours.

<script language=php>

set_time_limit( 10 );

while( true ) {
    echo "sleeping...<br>\n";
    flush();
    sleep( 1 );
}

</script>