It says right on the pass that it is good through April 15th. I've skied Crystal into June and even July (July 11th in Green Valley), but that was WAY back when. There was no Palmer Glacier lift, and no Pomas on Blackcomb glacier. The mountain is SO much better than it used to be: Grooming, lifts, lodges, etc. Alpental? They do have a HSQ there, a patio... but do they Winch-Cat the upper mountain anymore? No. Do they REALLY plan to expand? After 40 years, I really doubt it.
I was at Alpy yesterday. They could go a while. They get MANY more last-minute casual skiers there, which helps the cash flow. And they sell a lot of food and beer on the patio. The lot was so full (for a while) there was no place to park!