In non-story material referencing the party, they are alternatively the "Companions" if the time period is before the War of the Lance, or the "Heroes of the Lance" afterwards if the author prefers.
In game or in story, they have no official title prior to the war, or they are the "Heroes of the Lance" after the war. NPC's will recognize them as "Heroes of the Lance" post-war if you go by the Novels precedents.