How long is the queue and how many hours if we will buy the ticket directly in the station

From Jan 01 to 03, there is a 3 days holiday and thus there maybe many people in the station on Dec 31 as well. You may leave around 90min for it if possible. By the way, if possible, it would be better you can buy like a few days in advance if you arrive at China before Dec 31. Personally speaking, i think it would be safer.