Joseph, the people who date very short also live in societies where divorce is much more taboo (not that it doesnt happen, just that its not as rampant). People stay in terrible marriages to avoid the taboo of raising their kids alone.
You will never find out “everything” you need to know and short dating can work, as long as you have uncovered the most important things and are both being intellectually honest with each other. There is no magic amount of time.
Also, I had a friend who dated her husband for 3 months (short in my circles) and then got married 3 months later. Turned out he was addicted to painkillers. He was able to hide it quite easily. He even had just come out of rehab when they met. No one except his parents knew so all the research in the world wouldnt help. They got divorced (and thankfully didnt have kids).