As i did some more reading on Lync client functionality, i see the video/audio recordings are stored in the recording manager and can be configured on the client to publish them to SharePoint portal.
i see for IM messages, when conversation window got closed, it will be saved to the outlook conversation history folder.
can we write a custom extension using the Lync client API and capture the IM message conversation with the contacts and store them to the desired location (like sharepoint library or database etc.).