In Openflowplugin topology-lldp-discovery.xml lldpLinkAger value is hardcoded like
<bean id="lldpLinkAger" class="org.opendaylight.openflowplugin.applications.topology.lldp.LLDPLinkAger"
destroy-method="close">
<!-- Interval to send LLDP (five seconds) -->
<argument value="5000"/>
<!-- Expiration interval for aging out links (3 * the interval) -->
<argument value="15000"/>
<argument ref="notificationService"/>
</bean>

which we need to remove:

URL: https://github.com/opendaylight/openflowplugin/blob/master/applications/topology-lldp-discovery/src/main/resources/org/opendaylight/blueprint/topology-lldp-discovery.xml