I wouldn't worry about aftermarket HSF for non-overclocking unless you require something quieter, a custom form factor or possibly for cosmetic reasons.
Reliability-wise, material and manufacturing defects aside, semiconductors without consumable internal structures (EEPROM and NAND for example) will typically last 20+ years when operated within specs. My audio amplifier is over 30 years old, still works fine apart from switches that could use a cleaning and putting in some new input filter caps wouldn't hurt either.