Octalithium ceramics with their high stoichiometric concentration of lithium offer exceptionally high tritium breeding ratios (TBRs) in comparison with other candidate breeder materials for tokamak fusion reactors, this is especially true with incorporation of a neutron multiplier into the crystal structures. Although, there are concerns surrounding the stability of these materials at operational temperatures. Therefore in this paper, we explore the thermodynamic properties of a selection of candidate octalithium ceramics in low and high temperature regimes (0-1200 K) using density functional perturbation theory (DFPT). Enthalpies as well as Gibbs formation energies were used to distinguish candidates which may or may not be susceptible to degradation.