"The DNS cache doesn't ever flush, unless you explicitly tell it to or you make a DNS/networking related configuration change. DNS records have a Time To Live (TTL) value associated with them which tells a DNS cache how long the particular record is good for. Records in the cache are kept for their TTL, then re-queried.
On a Windows machine you can see a list of all the records in your cache along with their TTL by executing the following command at the command prompt:
You can force a flush of all cached DNS records using the following command: