Big White closes mid April, Whistler closes early June.
The condidtions right now are the best they've been since December. Head up now if you can. I'll be going up to Big White this Weekend.
I couldn't tell you how long the snow will be good for because this has been a wierd year. Last year the closing day was a nice powder day with at least 10cm's of fresh stuff. Other years there's barely enough snow on the ground to get down the hill.
The snow's almost always heavy at Cypress, Seymour, Grouse, get used to it.