You are the one that controls the game...it begins with you and ends with you. Tug is a great confidence builder, gets out a young dogs oral need for exercise and teaches some self control. The only warning I would heed would be:
NO tug during teething!
Two of my dogs won't play tug with me because I didn't do it early on, they let go and defer to me. They will tug with one another. I think tug is an important game for training & drive building.