Unless something deliberately catches Conan's attention and he decides to do an in-depth investigation, he will only be getting very general things from this. Perhaps background would be a better word than history. He can figure out things like hobbies, profession, if someone had traveled recently and where they had been, if they work with their hands, etc. But he won't be getting anything more specific than that. Its mostly useful as a way of impressing people with his detective skills and of figuring out when something doesn't fit in the middle of an investigation.