True, but this is an edge case that is unlikely given the toll that pregnancy takes on a woman's body and the challenges for the family. If you have kids, can you honestly say that you think this would be a good thing to try?

Another issue is where the parental-leave financial support comes from. Should it be the company's responsibility, or is this a government initiative to invest in the health of its citizens? Would you support the idea if the company had zero financial responsibility for the paid-leave (and only had to bring the parents back on once leave is over?)

I was not thinking so much in terms of financial difficulty, but in terms of changing company culture. A lot can change at a company in three years. You may have to completely reorient the employee. Or...maybe since the employee has been absent for so long, their position is no longer valued/needed. The company shifts in a different direction without the employee there to shift with it.

Can all jobs be easily replaced with a "temporary employee". If you have a lot of inside knowledge and training that allows you do perform well, it would take a lot of training to get a temp up to speed.

Also, three children may be an "edge case", but two definitely is not and it seems like the same problems would apply.

Unemployment benefits (to which you contribute with your paycheck when you don't have kids, fwiw) pay, not the company. A company just needs to hire a temporary worker three years in a row to replace you, if needed.