Your comment doesn't make any sense to me. A single kid sucks more time than you have in a regular day. You are sleep deprived, and in survival mode for the first part.

If you have a lot of kids, after a certain age, the older ones can start to help around depending on age. It's how humanity survives in self-sufficient conditions.

For serial kid rearing families there is a plateau in difficulty, and then a steady decline (depending on the personality and health of the kids of course).