I don't think any of them go round trip to the west coast. Generally there is a one-way repositioning cruise from the west coast to South America after either the Alaska or Mexican Riviera season so that they are in South America in their spring and summer and would probably not plan on going all the way north into winter weather. The return trip to LA or San Diego would then be in their late summer (our early Spring) when they are again going to Alaska or the other way to the Caribbean or Med.
The flight was not all that bad for us. 15 hours one way and 16 hours the other. We went on United and felt we had good service both ways, even if we did go tourist. We got bumped to Business class on our last leg home which did help a lot. A number of people used their frequent flyer miles to upgrade to 1st class or Business to get better seats.