In that case, it is less interesting. First, I have to find a ParknShop to buy the card, then I have to register it, and, maybe, I have to wait for approval of the registration before using it. Since I am just staying for a short time, I will not top it up to keep it alvie. The next time I come back to HK, I will have to buy another one. If I visit frequently, I will use up my quota of 10 registration for an individual. These considerations will not rule out buying one, because the price is so amazing. But, it requires some thinking. I probably won't go back 10 times, but who knows.