How long does thermal paste last and when to replace it

Thermal paste is one of those things people fit once and never think about again. That's fine for a few years. After that, dried-out paste is one of the most common causes of high temperatures, throttling, and systems that used to run cool but gradually don't anymore.

What thermal paste actually does

The surfaces of a CPU and its heatsink look flat but are microscopically rough. Without paste, the contact between them is full of tiny air gaps - and air is an extremely poor conductor of heat. Thermal paste fills those gaps, giving heat a direct path from the chip into the cooler.

It doesn't need to be thick. A thin, even layer is more effective than a blob - excess paste that squeezes out the sides doesn't help and can cause problems if it reaches components it shouldn't.

How long does it last

The honest answer is: it depends on the paste and how hard the system works.

Budget pastes - the grey compound pre-applied to stock coolers, or generic white paste - typically dry out and lose effectiveness within 2-3 years under regular use. They work fine when new but degrade noticeably over time.

Mid-range pastes like Arctic MX-4 or Noctua NT-H1 are rated for 4-8 years and hold up well in real-world use. These are what most people should use.

Liquid metal - compounds like Conductonaut that use gallium alloys - can last longer thermally but react with aluminium heatsinks and require more care to apply. Worth it for enthusiast builds and laptops, not necessary for most desktop coolers.

The biggest factors shortening paste life are heat and thermal cycling. A CPU that regularly hits 90°C and cools back down stresses the paste more than one that runs at 60°C. Laptops, which run hot in confined spaces, typically need repasting every 2-3 years. Desktop systems under light use may go 5+ years without issue.

Signs the paste needs replacing

Temperatures are higher than they used to be. If your CPU ran at 65°C under load two years ago and now hits 85°C doing the same tasks with the same cooler and clean heatsink fins, the paste is the most likely cause.

Thermal throttling has appeared. A system that stutters or slows under load when it didn't before, with temperatures spiking to 90°C+, is a classic dried-paste symptom.

Visible paste condition. If you remove the cooler and the paste has turned chalky, crumbly, or has separated into dry patches, it's well past due.

Age. If it's been more than four or five years since the paste was last replaced - or you've never replaced it and the machine is that old - it's worth doing regardless of current temperatures.

How much difference does it actually make

On a machine with degraded paste, the improvement from a fresh application can be significant. Drops of 10-20°C on the CPU are common. On a laptop that's been running hot for years, it's not unusual to see 20-30°C improvements.

On a system where the paste is still in good condition, switching to a premium paste from a budget one might yield 2-5°C. Worth doing if you're already in there, but not worth dismantling a healthy system for.

The repasting process

For a desktop CPU: remove the cooler, clean old paste from both the CPU lid and heatsink base using isopropyl alcohol (90%+) and a lint-free cloth, apply a small amount of fresh paste (pea-sized in the centre is a reliable method), and refit the cooler. The paste spreads under pressure as the cooler is tightened down.

For a GPU: more involved, since the cooler is typically held by multiple screws and the card needs to be removed from the system first. The process is the same once the cooler is off, but you're working on both the GPU die and usually the VRAM chips, which use thermal pads rather than paste - check whether those need replacing too while you're in there.

For a laptop: varies significantly by model. Some are straightforward; others require near-complete disassembly to reach the CPU and GPU. If you're not confident, it's a job worth handing off.

When to send it in

If you're comfortable with a desktop repaste, it's a manageable DIY job. GPU repasting and laptop repasting are more involved - a GPU cooler done carelessly can void a warranty or damage the card, and laptops can be fiddly enough that forcing something causes more problems than the paste itself. We repaste CPUs, GPUs, and laptops regularly as part of general servicing, and can combine it with a full clean and thermal check at the same time.