outofsync,
I take that point - if the disks are isolated from airflow, then conduction would probably make for a better way to lose the heat to the air from the metal around that's now in better contact.
I buy the minimum temperature argument too - while that temperature will be reached and passed very quickly in a big stop, in F1 racing, where inertia is less, sharply increased bite is reported after about half a second, once a threshold temperature of about 500C is exceeded - although the brakes are working cooler, or they wouldn't heat so fast.
There's a A380 brake test dynamometer video that heats them up fast, presumably from cold over 25s or so. The bulk of the stopping is done with the brakes visibly yellow-carbon burning hot.