Well, make them stop it :-) If you think you could get the time, I have a hostnames VBScript I collected from somewhere that will do it for you. It does take some time though...

>Hi Jim. Darn cache is cleared to frequently.
>
>>Try "arp -a" from a command prompt and see if it shows up. If not, build a batch and ping the entire subnet. This should make it appear in the ARP cache.
>>
>>>I've discovered a rogue device on our network and I know it's mac address (using Netstumbler). How do I determine the IP address from the MAC address?