Customers always would like to keep store their all document versions but they don’t know how much space would take to keep storing the versions on the document.Document versions are always a bottleneck for the SharePoint administrators interms of sizing the quota limit.
Mike Mukalian had written an excellent powershell script to delete all the versions of document/files in the document library. For more information, please take a look at his blog entry.
Also, SP administrators would always like to automate this operation on a periodical schedule. In order to do that, 1. Create a scheduled task to run the script nightly/your own schedule and configure Powershell permissions on the server (run Set-ExecutionPolicy RemoteSigned from a Powershell prompt).