I've read https://parenting.stackexchange.com/questions/1908/what-is-the-least-problematic-age-difference-between-siblings but I had a different question.

That question is rather "from a child's point of view: what age would you prefer your siblings to have". 

Mine would rather be: 

 1. Are there any advantages/disadvantages of becoming pregnant right
   after giving birth?
 2. How much time should be left between pregnancies? Why?