Question : Do you have money enough to replace a working pc?
Anwer 1 : Yes. Ok then, you've had it since 2012 and it's getting old and slow compared to new and heavy games, go for it for as long as it lasts. Not going to hurt anything but your wallet.
Answer 2 : No money. Ok then, you need the pc to last long enough to give you time to save up for replacement, so don't OC much at all, because you have no idea how much life is left in the board, caps, psu, cpu etc and you don't have realistically nearly enough cooling.
Simple.