Fun fact: I once mathed out how long a lifespan I would need to expect before I'd be willing to spend 18 years of it raising a child. It came out to 14,040 years.

(This is assuming that women in my family can generally expect to live to be 90, and I would be willing to spend six weeks at childrearing, tops. Though if you assume longer lifespan = longer maturation period, that throws the math off.)