Since you are on 4.1, you can control the purging using CMC. You can specify the days you want in Audit DB. BO will automatically takes care of purging Audit DB what ever the number of days you need.
Check the Admin guide for list of Audit tables and move them to new schema . Login to CMC. Auditing
And change the Audit DB settings in CMC.
Ajay's screenshots are base don BO 3.1 , not 4.1.