The A320-series is very susceptible to hot brakes. That's what the Captain was talking about. Monitoring brake temperatures is something that is done on every takeoff, taxi, and landing on the A320 series.

Significant heat is generated in the tires while taxiing in addition to the heat from the brakes used during taxi. More heat is generated in the tires during the takeoff roll. It takes a while for the wheel/brake temperature to peak--up to 15 minutes--after the landing, taxi, or takeoff that generated the heat.

Did you takeoff to the north from Seattle? The taxi to runway 34R is downhill requiring more brake use.