Collecting Train Tickests

Hi I wanted to ask i'm going to be in Beijing on 20/09/2015 and i wanted to know if I book the tickets now will they wait for me till then in the station. I f so I'll book them I need Beijing-Xi'an on 26/09 and Xi'an-Beijing on 29/09 since i won't be in china till the 20/09/2015 i can't collect them before this time, but still i prefer to buy them as fast as possible.
Is it possible to collect tickets 2 months after ordering them?