While they claim "light lubricant", it's also a very temporary lubricant. As I've stated previously, I've personally dealt with the effects of leaving WD-40 on an item for an extended period of time. Specifically, I'm talking about guns, though the same effects would clearly be exhibited for any mechanical device. After a year or two, it turns into some sort of sludge-like varnish that is almost impossible to remove! I've had to soak guns for a week in solvent to loosen the WD-40 before I could even disassemble them!
IMO, it fails miserably as a lubricant.