Well for one, Lake Louise had a week last May where it was free skiing the whole week for anyone with a season's pass to any ski hill in North America.
A ski hill can only stay open for so long, usually in May, many hills are closed because many people don't want to ski any more. If only the locals and pass holders are skiing, they make no money. So even if it dumps 5 feet on closing day, they're probably still going to close.