Come with me to the Dark Side, Luke...

I was reacting to the original statement in the training film which stated that the reason for not continuing the search was the coming of night. When I was active, night capable aircraft were a rarity, but ground teams could certainly have been dispatched. Our motto was "Search is an Emergency" and we had numerous examples to cite. I woud certainly agree that rescuers must be properly trained, equipped, and briefed on conditions surrounding the operation

I agree that many factors influence the decision to activate, and your example of avalanche terrain is a very good example - pay attention to the hazards (Avalanches are rarely a problem in southern Arizona - we would probably welcome the moisture). OTOH, the traditional alpine start, 2 AM or so, has traditionally been dictated by the likelihood of avalanche, cornice collapse, etc. being less likely in the wee morning hours, and highest in the afternoon.

We were pretty aggressive about responding to a search aggressively. Many times that immediate response was unnecessary, but from time to time, lives were definitely saved and delay would have incurred more suffering, if not fatalities.

In my experience, we did lose one member, a very fine person, who contracted Valley Fever while driving on dusty roads during a protracted training exercise, although it took several years before he succumbed. He and I both attended the only SAR related memorial service I have ever attended, one held for two AZ Highway Patrol helicopter pilots who crashed on their final mission, having just discharged several members of our group.

You must consider many factors in going into the field, but darkness is just one of them, and often not that important.