Quantity my friend, quantity. If the beer were fully consumed while still optimal, that would be evidence of inadequate supplies. Those round igloo coolers with the spout on the side could hold a nice quantity, but did not excel at insulation.
I went to a game in the mid-eighties where I sat beside two elderly brothers. One had been retired for "about 5 seasons" and the other had just retired. The old pro was showing his brother the ropes. One of the tricks was to put 4 (not 3,not 5) ice cubes in your igloo to keep the beer cold.