Melt Pool dynamics determine the features of the part produced in the SLM. The question is about the initial and ending melt pool shapes during the 3D printing and how much time would it take to reach the equilibrium pool dimensions?
It actually varies case by case. That is why so many numerical simulations were done in this field. So, you can search through literature to find your case or performing experimental heat gradient analysis on you process.
At the end of August we are going to publish a study on this topic. We are still analyzing the laboratory results with the University of Genova. We'll publish it on our blog: https://www.tav-vacuumfurnaces.com/en/blog.aspx