The free beta has some issues and is not upgraded, I gave up on it, but the Pro version lets you use it 40 times before it expires. No time limit otherwise. The Pro version has all of the current features and gets updated. When/if you pay for it you get an email that will eliminate the trial counts. I'm still figuring the Pro version out.
There is a CamBam forum on CNC Zone where you may get some better answers.