We will be staying at WL 6/20 - 6/26 and when we took a vist to WL last July 4th, the fireplace was not on . . . .I would assume they only have it on during the cooler months.
Checked in June 29th last year and it was going--we had a terrible rainstorm on that day and our room was not ready so we sat next to the fire to keep the kids warm until our room was ready. When we there at Easter they were all working as well ( both WL and VWL)