Hi Hitesh,
The records are stored indefinitly unless you configure DB purge,
You can use Automatic Database Purge to delete CAR Records older than an specific time using Manual purge under ART tool.
If you are referring to the rows in DB.
The Max number of rows in tables (Billing_Data)
for ART database, this value is limited to 2,000,000 rows for the billing table. Any records above this limit are deleted.
You may see CAR Database Alert
Max number of rows in Billing Table*
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_qanda_item09186a008020650a.shtml
http://www.cisco.com/univercd/cc/td/doc/product/voice/c_callmg/3_3/service/serv334/ccmsrva/sacar2.htm#wp1094892
Let us know if that was your question.
Gonzalo