Yes, some people like to boil a very small portion of the extract for the full duration and then add the bulk of it at the end. I don't find that to be necessary. When I do extract, I steep my grain as usual, bring to boil, add hops per recipe and boil down to the last ten minutes and add the extract. I do like to boil the extract for just a few minutes to make sure it gets sanitized. I also don't want to be trying to add my finishing hops and extract at the same time. This method also lets the liquid boil down so there is more room in the kettle when you add the extract = less chance of boilover.