In order to maintain long-term size homeostasis, cells must on average double in size before they divide. In most organisms, this is accomplished by establishing a dependency on growth for cell cycle entry. read more
For every cell that dies a new one must be born, so there must be at least between 50 and 70 billion cell divisions to replenish these cells in an adult human (no net growth). But then I remembered erythrocytes. read more