IMO, the 120 hour recommendation is probably a conservative estimate. The manufacturer has no reason to cut corners here because they're the ones who'll have to do the warranty work if that recommendation is too long. Will it hurt anything to change it early? I doubt it. Will it help? I doubt that, too.
The engine may or may not come from the factory with break-in oil. If it did, I'd leave it in for the recommended time, too. If not, change as early and often as you like.