Seems fine to me.

I'd add one qualifier to it. Currently it has the possibility to completely destroy a weapon. You touch an opponent's sword and it might just shoot off into the sky. By the time the effect wears off, the sword falls and breaks. This would suck to happen to a PC, so you want to prevent it. Easiest method to prevent it is to allow the sword to save every turn. Usually magic items use their wielder's saves, but they also have their own saving throws. That way it will hopefully make the save before it goes high enough to reach terminal velocity and take 20d6.
2+(half creator's caster level) if you want to throw it in the description as a reminder.