PCI Compliance and SEPM retention logs

Hi, can anyone tell me what the best settings are for about 150 different devices to retain logs for 365 days?  Right now, the log file size is set to 256 KB or 365 days, whichever comes first.  We just had a PCI Compliance Audit and we were told that 256 KB is too small too keep 365 days worth of logs, thus we believe we're going to fail our audit (it will cost us big bucks if we fail!).

What should we be setting the log size to without causing our database to exponentially grow out of control?

Thanks!