Since this question comes up every now and again, here it is with the answer:
Q: If a file is deleted or obfuscated from a local machine, how long will the local approval stay in the endpoint's cache and Bit9?
A: There are two types of local approvals in terms of how Bit9 categorizes them: A "Normal" Digital Antibody (dab for short) and a "Priority" dab.
A priority dab is directly traceable to an event like initialization, manual approval of a file from the console or dascli, etc. Priority dabs have a default expiration time of 14 days if the approved file is deleted.
A normal dab is created "indirectly", the most common being a rule. So if you create a rule that says "Locally approve all files signed by publish TRUSTME, INC.", then it would be a normal dab. Since the rule to approve it is still there, there is not nearly the need to retain the approval, so the default expiration time is 3 days.
Both of these time periods can be changed, but changing them should be considered carefully, so please contact Bit9 support if you need to change these values.