Do ski resorts open terrain and lifts when there is enough snow or on a certain date?

I'm going snowboarding in Breck in early December and have been seeing all the snow reports, but why aren't lots more runs open yet? I think there was less than 30 inches base depth last year and more stuff was open.|||They gotta build a base up, if it's too warm and they get snow anyways it's hard to create an ice base under the actual snow base so that it doesn't just melt. They'll open up more progressively as they can get a solid base throughout the entire mountain, otherwise you'd be riding on grass the first warm weekend of the year|||From my experience, they do both. If there's enough snow they'll open early. But also at the same time they will open later if not enough snow. I have found some that open no matter what on a certain date to get into the routine of ski-season if not enough snow to open early.