This paper presents the results of a study on the heat deflection temperature (HDT) and Vicat softening temperature (VST) of the LH285 MGS aerospace polymer resin, used as a matrix in ablative shielding composites. This topic is particularly relevant because, during ablative testing, the composite material undergoes partial combustion (ablative layer), while its remaining sections are exposed to elevated temperatures, leading to changes in viscoelastic properties that depend, among other factors, on VST and HDT. In this study, the authors examined aerospace resins cured under various conditions as recommended by the manufacturer. In addition to assessing changes in thermal properties due to material conditioning, the study also investigated the effects of heating rate and applied load magnitude, following the applicable standards for this type of material. The results indicate that resin heating influences HDT and VST values. Additionally, the indentation shape in the material varies with conditioning temperature. However, the choice of heating rate and load magnitude had a relatively minor impact on the results.