the cheapest thermal compound
If the CPU / GPU exceeds its acceptable temperature, it will slow down (to prevent overheating). So we need to replace the thermal compound. Replacing the CPU is not difficult. You can do it yourself if you have a hand. This new thermal compound can reduce the temperature from 5C to 20C. What types of thermal compounds should be used? Prices are not a big problem. You can use any brand you like, from Chinese to a thousand big brands like Cooler Master.
Even the cheapest thermal compound on the market, once applied, can cool down for another year. Be careful when using it to prevent it from protruding from the back of the CPU. Otherwise, it can cause unwanted problems. It is enough to put two sizes as shown in the picture. In short, replace the CPU thermal compound every year and a half. It is not difficult to do and it does not cost anything. For graphics cards, it should be done after the warranty period expires.