You want to place your tipis near the buffalo herds to support your tribe, but you have to be able to continually maintain your tribe, which gets harder and harder as the game progresses. As long as there are buffalo near your tipis, there is no problem, but be careful that you don't fall behind the herd migration!
At the end of the game, the player with the most tipis that traversed all the way across the plains is the winner.