Hi Rahul,
Nico is right as usual, and it's a nice way to go.
You also may look at this 2008 SAP paper explaining how to archive PSA tables. You may end up with some errors when starting using it but with a developer, you'll get it fixed.
Thanks for asking your question here, as there is a good reason for archiving PSA table rather than deleting them: when your BW ODS or Cube is tax relevant (with profit margin or transfer pricing information for example), then some law force you to trace the data since the origin of data. So a missing PSA could be considered as a gap in an audit trace...