Guitar Hero Will Charge a Second Disc Import Fee for World Tour and Smash Hits

Disappointed that Guitar Hero World Tour only exported 35 out of 86 tracks? If additional songs are licensed and become available for disc importing in the future, you'll have to pay another re-licensing fee for those new songs, according to official Guitar Hero Support information.
The same goes for exporting Guitar Hero Smash Hits, which only offered 21 out of 48 on-disc tracks.
The official GuitarHero.com FAQ states:
Will the Disc Import offers available now be updated in the future? Will new songs be added?
No. If new songs become available an additional import will appear in the Import Offers list. There will be a nominal re-licensing fee for any additional offers.
