I was under the impression that it is not cumulative. As in if you progressed to Platinum and didn't use your upgrade before subsequently moving to Concierge then you would still only have 4. Similarly if already Concierge and earning 601 the following year you don't get an additional 1 upgrade or if you retain concierge without having used any upgrades you don't suddenly have 8 upgrades available. I thought it was 4 per year as concierge and 1 per year platinum in a 'retaining' situation and only in an upgrading year could you have the possibility of obtaining and using more than that. I would love if the opposite were true and they were cumulative in which case I'd be sitting on 12!

I'm not sure on any of the above its just my reading on their rules and am happy to be corrected.