It’s important to keep your system away from dust. That’s why I clean my machine regularly. Not only that I usually buy old consoles, it’s even more important to clean them before the startup.
Same thing with the thermal paste. As you can see on the pictures below I’m removing the old paste and cleaning up the old mess. After that is done I’m placing some new paste on the CPU and GPU.
Here you can see the difference on the cooling after I cleaned up the system and replaced the old thermal paste with new one.