Purpose: To present a method for predicting the lifetime of dental materials using in vitro thermally accelerated aging. The technique was tested to compare the behavior of three resin base materials for dentures. Materials and Methods: Bar-shaped samples of the polymethyl methacrylate (PMMA)–based resin Probase Hot (Probase), CAD/CAM disk Ivobase CAD (IvoCAD), and high-impact resin IvoCAP were aged in artificial saliva for 15, 30, 45, 60, 90, 120, and 180 days at 55°C, 75°C, and 90°C. Flexural strength and surface roughness of the three resins for each aging duration and temperature were measured for three samples (n = 189). Using the time-temperature equivalence principle and the Arrhenius model, a master curve was constructed, the activation energy of the simulated aging process was calculated, and the lifetime of each material was estimated based on degradation of flexural strength value over time. Results: The mean initial flexural strength was 87.98 ± 7.37, 79.35 ± 10.01, and 97.31 ± 4.97 MPa for IvoCAD, IvoCAP, and Probase, respectively. Activation energies of the aging in artificial saliva were measured at 81.9, 82.6, and 66.2 kJ/mol, respectively, and average lifetimes at 37°C were estimated at 19.5, 14.4, and 9.2 years. Conclusions: In this first approach to estimating the in vitro lifetime in artificial saliva of resin-based materials for dentures, the three materials met the expected criteria, validating the estimation method. Therefore, thermally accelerated aging and the Arrhenius model could be an interesting tool to add to routine tests used to validate new polymer materials and manufacturing processes.