Find out max amount of TS licenses used

Hi

I have to migrate our current TS server, based on Windows Server 2003 Standard to a new TS using a VM with Server 2012R2 Datacenter.

Currently, for 2003 server, we've 30 device CAL and 30 user CAL, but I'm afraid we never used that amount of licenses so, now that we must buy new CAL licenses, the question is easy.

Is there any way to find out how many CAL licenses have been used concurrently (either user or device) for the last year, or even since the beginning of time, so I can figure how many new CAL licenses must we buy?

Thanks