How often are domain names updated in address book?

I've noticed that the SRX allows domain names to be added to the address book, as follows:

security-zone untrust {
 address-book {
  address SomeHost {
 dns-name example.com;
}

But how often will the Juniper device check which IP the domain resolves to? I.e. if example.com changes the IP that it resolves to how long before the Juniper device notices?

What I'm trying to do is create a rule so that some staff can access our network from home. They don't have static IP addresses but they do have dynamic DNS, like the no-ip.com service, where they get a domain name which follows their IP.