Preferred retention period of virus definitions in servers

Hi friends,

I'm using symantec AV 12.x. Facing low disk space issue most of the server due to the virus definitions as generated in the following path,

C:\ProgramData\Symantec\Symantec Endpoint Protection\12.1.1101.401.105\Data\Definitions\VirusDefs. I need a proper retention period of those definitions that I can delete old definitions to avoid the space crunch issue in servers. I'm excpecting a solution that will not affect a smooth functionality of SEP in servers. 

Regards,

Jaril