O principal fator no overclock é a qualidade da CPU que você recebe, o que é uma questão de pura sorte.
Cito Riscos de overclocking :
Usually processors in the lower range are produced with the same manufacturing process as the CPUs sold in the mid to high range. The higher rated CPUs are factory overclocked and tested, then sold for a premium. Many users will buy the cheaper processor and over clock it to nearly the same speeds of the premium CPUs. This is a great deal if and only if you are lucky enough to get a CPU that just missed the premium cut during initial factory testing. Sometimes, you will be stuck with a CPU that only over clocks slightly above its rating.
No entanto, você deve estar avisado de que, com o overclocking, corre o risco de um dia esgotar completamente sua CPU. Felizmente, há sinais de alerta que não devem ser ignorados, como o ocasional acidente inexplicável.