Thermal paste should generally be changed every 1 to 3 years, depending on various factors such as the quality of the paste, the intensity of CPU use, and environmental conditions. For normal home or office use, changing thermal paste every 2 to 3 years is usually sufficient. For high-demand systems or lower-quality pastes, it might need to be replaced every year or even every few months. Signs that thermal paste needs replacement include rising CPU temperatures, drying or cracking of the paste, poor performance, and unusual fan noise. Regular monitoring of CPU temperatures is a practical way to judge when to replace it rather than relying solely on a fixed timeline.