If you wanna do a late season, Changbaishan would be your best bet. The west hill (Xi Po) opens till mid May with untouched pow on daily basis.
Yabuli is only good after Chinese New Year, lots of fresh pow with no wind. Any time before that just icy bitch
Changbaishan Wanda is better than Yabuli before CNY I would say.
Longest run is Beidahu line 14, 3.2 KM blue run
Or, wait till end 2014, there is a new one building by Wanke with Japan's Prince hotel group. They claim to be the largest resort in China which locates in Jilin province