Intel processors are warranted for 3 years under a maximum load temperature of up to 105°C.
That being said my 1st gen i5 480M laptop which hit 80°C at load for several hours while streaming still lasts well till now with not even a single MHz drop for 6 years.
Even a tower aftermarket heatsink would keep the temperatures in check. At about 70-80°C full load an overclocked Intel processor could last more than 5 years whithout degradation (i5 2500K, i7 2600K).
Your CPU which is at stock and not overvolted, and also under a liquid cooler would easily last you 10-15+ years without any noticeable degradation. And even if there is degradation, a small drop of 100 MHz would make it run for another 10+ years at stock clocks. That means your processor would last long before it fails even at 24/7 server utilisation, and by that time you would already have upgraded your CPU.
If you really fear even a small degradation, or plan to use it for 100+ years for whatever reason, undervolt your CPU by a few notches. Maybe 0.002-0.004V It would run cooler.
Your hard disk will fail first. Backup.