Hi Shivani,
After posting my response here, I sent it to four Developers for their thoughts regarding my answer. Rather than state specifically that I was wrong, they politely stated that they thought the retention period was 30 days, but needed to check out the mechanism on how that was accomplished.
I have since gone back to the documentation and found the following points:
Configure CA TDM Portal for Deleting the Purged Reservations
Configure Dynamic Test Data Reservation Service
Use APIs to Design and Consume Automated Test Data Services
However, these do NOT speak to the general question that you are asking. I am continuing to explore that in depth with the Developers. However, in the mean time, you do know that the jobs are kept on the hard drive and that we do not clean up those jobs. Have you explored this aspect? Have you decided on an approach to clean out the old results?
Cheers!
Les