I'd be willing to bet the "hit the countermeasures immediately" reflex was because they were landing. Low altitude, low speed, no ability to maneuver. If somebo

I'd be willing to bet the "hit the countermeasures immediately" reflex was because they were landing. Low altitude, low speed, no ability to maneuver. If somebody was shooting at you in that situation the missile would be on you in seconds and countermeasures are the only chance you have. In a more normal combat situation there's a lot more human judgement needed in the use of countermeasures. For example if a fighter locks you up and fires a missile from 50 km away and you fire chaff immediately you might temporarily disrupt their lock, but it's likely that the chaff will disperse and they'll be able to re-lock you before the missile gets anywhere close. You can't just fire them off continuously because it's a limited consumable.