Will CPU lifespan or stability be affected under high temperature?
Intel
As long as the temperature is lower than the original standard (105 or 100 Celsius degrees) regulated by Intel, the CPU lifespan will not be affected. The CPU has its own protection system/mechanism. When the core temperature exceeds the set temperature, the power will be reduced to maintain a safe temperature. The temperature may vary, depending on the processor and BIOS settings.
The CPU has a Turbo Boost function, which will be adjusted according to the use situation. When the CPU starts the Turbo Boost function, the power and temperature will rise. This is normal.
Availability and frequency upside of Intel® Turbo Boost Technology state depends upon a number of factors.
When the processor is operating below these limits and the user's workload demands additional performance, the processor frequency will dynamically increase until the upper limit of frequency is reached. Intel® Turbo Boost Technology has multiple algorithms operating in parallel to manage current, power, and temperature to maximize frequency and energy efficiency. Note: Intel® Turbo Boost Technology allows the processor to operate at a power level that is higher than its TDP configuration and data sheet specified power for short durations to maximize performance.
You can refer to the below link for more detailed information:
Information about Temperature for Intel® Processors
AMD
AMD Precision Boost Overdrive (PBO) and Precision Boost (PB) are integral components of AMD’s automatic performance enhancement technology. When the system detects a short-term demand for additional processing power, the processor dynamically increases its clock speeds and operating voltage in real time, based on its built-in algorithms and platform conditions, including temperature, power consumption, current delivery, and motherboard power capabilities. Because these adjustments occur within milliseconds to seconds, power usage can rise sharply over a very brief period. As a result, monitoring utilities may frequently display sudden spikes in temperature.
Such transient temperature increases are a normal and expected outcome of PBO/PB operation.
AMD’s engineering team has repeatedly stated that, when PBO or PB is enabled, the processor’s boosting algorithm is designed to maximize performance within the limits of the cooling solution available. As long as the processor remains below its hardware-defined thermal threshold (Tjmax, typically around 100°C to 105°C depending on the processor model), it will continue to opportunistically pursue the highest possible performance. The processor incorporates highly sophisticated and stringent protection mechanisms, ensuring that temperature fluctuations within AMD’s official operating specifications have no adverse effect on processor longevity or system stability.
You can refer to the below link for more detailed information:
AMD Ryzen™ Technology: Precision Boost 2 Performance Enhancement