All my first year finals were essay based, and I did very well. Midterms this year included a lot of objective testing and I did, not quite so well. So though I assume that previous grades plus similar effort equals similar result, that assumption presumes all other factors remaining unchanged. I do know that the guy who was doing the best at midterms 1L really fell down the rankings at finals, maybe too sure of himself. So I'd say just keep plugging along and doing what you are doing.
Usually when my profs say this same phrase they mean indicator of an ability to be a lawyer. Law school exams do not simulate practice. So there will be a lot of mediorce students who are amazing lawyers. Meanwhile we all suffer at the hands of a few profs who were incredible students, but have settled in to be mini-tyranists in the classroom.