@Override
    protected double maintain() {
        expireReserved();
        return (deprovisionRemovable() + pruneReals()) / 2;
    }
Periodically expire load balancers and de-provision inactive ones.

Load balancers expire from the following states:

{@link LoadBalancer.State#inactive}: An application is removed and load balancers are deactivated.
{@link LoadBalancer.State#reserved}: An prepared application is never successfully activated, thus never activating
                                     any prepared load balancers.

@author mpolden
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/maintenance/LoadBalancerExpirer.java