Metallic thermal protection structures of reusable high-speed vehicles experience aerodynamic heating, high-temperature hold, and cooling in each flight mission, and the hot and cold faces accumulate different temperature and plasticity histories; after multiple missions, the elastic modulus, yield strength, cyclic hardening parameters, and thermal conductivity no longer vary only with mission count, but form a spatial field varying jointly with position and mission count. What effects such mission-to-mission, spatially non-uniform property evolution brings to structural responses, and what is missed in design when material time-dependence is not considered, are questions to be answered in the design of reusable thermal protection structures. This paper establishes a mission-to-mission, spatially local property update method: each mission solves the thermo-mechanical response with the current property field; at the end of the mission, the thermal exposure and plasticity accumulation at each integration point are extracted, and the material properties are updated through an evolution relation driven by the dual histories, for use in the next mission; the method is embedded in a non-isothermal Chaboche–Perzyna viscoplasticity program. Under a unified mission profile, a thin plate, a perforated plate, and a thick plate are computed for 50 missions each, with pointwise update (Case C) as the reference and no evolution (Case A) and uniform update (Case B) as comparisons. The results show that ignoring evolution gives higher structural stresses than the evolution-tracking case, with the strength-check deviation not exceeding about 4% within the 50-mission window; this is conservative for strength checks, while it continuously underestimates the damage accumulation, with the maximum accumulated equivalent plastic strain underestimated by about 12% at the thin-plate hot face and about 5.4% at the perforated-plate hole edge, biasing life assessment toward the non-conservative side; uniform update deviates by only 0.4% in the thin plate with a mild degradation distribution, but produces 14%–19% stress deviations in the perforated plate with concentrated degradation and alters the temperature field itself. The degradation amplitude assumed in this paper is weak (strength-type parameters decreasing by no more than about 11% within 50 missions), and the above conclusions hold under the current assumption and case-study conditions. The results provide a basis for the thickness design, in-service inspection location determination, and reuse count assessment of reusable thermal protection structures.