If I book my tickets on Travel China Guide, does that guarantee my ticket purchase?

I'm planning a 3 week trip around China. From Guilin to Changsha to Xi'an to Chengdu. I'd like to get all the tickets bought before I depart for Guilin. But the time I travel to Guilin is more than 20 days away from the time I travel to Chengdu. If I book tickets on Travel China Guide before the 20 day ticket sale window, am I guaranteed to have those tickets?