A. Games rarely ever make it to 15:00.
B. If they do, in most cases whoever got sponsored the first time probably already has really good stuff because he's probably pretty good, so he's probably going to win with or without the sponsorships.
C. Sponsored items really don't do much to help you win a game. 5 arrows aren't THAT big of a deal against a guy in full iron, at the point of the sponsor items refill, the person probably has at least an iron sword if not a diamond one, full iron and a bow which makes sponsoring iron and bow useless, and any of the food will also be useless. That essentially leaves the cake, which can be used for other purposes, and the enderpearl, which has one use. It isn't that big of a deal. I said all this in my original post, if you bothered to read it, which it seems like you didn't at this point.