Message Monitoring - How long do the message logs stay?

Hi,

I know that ' Message Monitoring ' shows all kind of messages(both synchronous and asynchronous).

But how long does it keep these messages in the store. If i want to get a report of the messages sent 2 months ago does message monitoring allow us to get that list.

Is there any background job which deletes the previous messages based on some time interval .

Thanks Rahul.