If you're querying the whois data for localhost and the local machine is configured correctly, that name will always resolve to the IP 127.0.0.1. The whois-lookup for 127.0.0.1 will stay the same until the owner of the range this IP is in (127.0.0.0 - 127.255.255.255) changes (in this case extremely unlikely) or the range itself changes (also extremely unlikely in this case).

If I misunderstood your question, please clarify.