In my case ScratchX lasts closer to 3 months. Eventually it loses its transparency or it washes away, I'm not sure. But if you put a good wax coat over treated scratch, it lasts even longer. Yes, you'd mostly likely to re-apply the stuff every second or third wash, but IMHO it depends on the car's color. Mine is white metallic, so it doesn't show very much.
It is worth a try anyway, other then chasing every little scratch with rubbing compounds and polisher.