I am reposting a response by joshb earlier:
"Check the file <SMVI install dir>/server/etc/smvi.override. See if this file exists and contains the entry 'vim.client.log.verbose=true'. If it does, either add a '#' to the front of the line or replace true with false. This entry will load every SOAP request we make to VC and can increase log file sizes."
Currently, we are restricting the log files to 20MB and will retain them upto 7 days.