以前看本版说amex多次升降级拿bonus，都是什么卡？
我每次收到target upgrade offer (business gold upgrade to business platinum),
小字都写Offer is available for first-time upgrades to the new Business
Platinum Card only and for one Card account only. 这样就不能第二次拿upgrade
bonus了对吧？2016年拿过一次
