Need info-How long the deliveries and logs exist in the ACS

Hi,

As day by day the deliveries and broad logs etc.. increases the size of the Adobe campaign standard system, Is there any standards to maintain to purge  the data of delivery logs,deliveries  or system will delete  automatically the old deliveries and broadlogs  based on some configurations?

It would be helpful for us to reduce the performance by doing purge of data.

Thanks,

Sivaramakumar P