OEM has a locked down BIOS, no OC'ing.
Custom built rigs have unlocked BIOS, so we play with the settings, it's unavoidable.
To OC a system you advance the settings until it crashes, then adjust again or back them off.
So a custom built system will have more crashes but, will run better
This usually requires more voltage which produces more heat which degrades electronic devices, we all know that and OC anyway.
If you OC with EIST (speed step) enabled your system will run at lower voltage and lower heat most of the time, making it last longer
So it's all good, and we get to have fun.