Is this standard behavior?

[Rasmus Aaen]

Hi,

We are running Bind 8.3.1 on a couple of Win2K servers for about 200
domains. All domains have the same soa values:

Refresh: 7200, retry: 3600, expire: 864000, min. TTL: 43200

I noticed that the slave server updates the "modified" time on the zone
files only after the zone has expired and been transfered again. It is my
understanding that the modified time on the files should be updated every
two hours (7200 sec.) in our case.

In the logs I see a message that the zone has expired, and then the zone is
transfered from the master and loaded. This really bugs me, since if the
master server goes down, the slave will start expiring zones too early.

Is this default behavior, or is something wrong?

Thanks

/Rasmus