Hi Stefan,
Unlike the moving magnet scanners (Cambridge 6800 and its derivatives), the G120 has no thermal limitation to worry about. Even at maximum current, the scanner will only be required to dissipate around 2 watts. And if your scanner amps put out a nice clean signal, you will never wear out the bearings.
On the TurboTrack, we used to get 30K or greater out of G120 scanners. The question is, how good are your scanner amps? If you have really good ones (like the TurboTrack), then you can get some decent speeds, rivaling 6800 and derivatives. If you don't then frankly you will be lucky to get 12K out of them (which was the industry standard speed for more than a decade)...
Best regards,
William Benner