With every cleaning we replace your thermal compound. It is essential to the cooling of your system that this compound does not dry up. If your system is not in a well ventilated area or in a area of high dust, it is likely yours is drying sooner than it is rated to.
Thermal compound is a very high-heat conductive adhesive used in high-performance electronic equipment in order to improve heat conduction. The thermal compound helps in filling microscopic gaps, especially on heat sinks, which trap air in them, thus increasing the heat conduction. By helping to provide a reliable and long-lasting interface through efficient heat management, the thermal compound also ensures better and longer performance of an electronic equipment. Thermal compound is also known a variety of terms, including thermal paste, thermal grease, thermal gel, thermal interface material, heat sink paste, heat paste and heat sink compound. -Techopedia