I think the larger question is: why book early for a ski trip at all? I'd rather pay more for a last minute fare than make a trip somewhere and have to ski lackluster conditions. Given the price of lift tickets, paying an additional $100 bucks for an air fare does not seem like too high a price to pay for powder versus crude, cement, ice, chicken heads, etc
If it's just you and your wife, that's doable. But if you are coordinating with with 5-50+ people (possibly sharing rental cars, hotel rooms/condos/houses), that's not doable. Depending upon how remote the area you are visiting, hotel rooms and plane seats fill up, advanced lift ticket deals expire, etc. Depending upon the airline, last second airfare can be much, much more than $100 extra. Toss in possible last second prices for lodging, car rentals, lift tickets, etc., and the extra $$$ can really add up.
Plus if you fly Southwest, you can cancel your flight for free and apply the travel funds to a future trip.