A temperature maintenance and/or possible heating apparatus for long products, continuously cast and sheared to size by means of shearing means so as to define segments of bloom, said apparatus being disposed between a casting machine having a first casting line and a second casting line, and a rolling line disposed downstream of the casting machine in order to make long rolled metal products. The apparatus comprises a first furnace, a second furnace and a transit tunnel. The first furnace is provided with a first introduction rollerway. The second furnace is disposed upstream with respect to said first furnace, provided with a second introduction rollerway. The transit tunnel is located aligned with said first casting line, adjacent and parallel to the longitudinal extension of the second furnace and upstream of said first furnace.