I suspect you're right. My comp is a laptop G4, and it's been working all day on a monster (about 16 hours I think), and it's only 31% done.
I have a G4, too, and it's been working for over 2 days (!) and is just over 1/3 done. Maybe they like Macs for the monsters! It would have been more gratifying to start small, though. :-)