To play all of your games on the list at full speed, you will need to overclock to about 4.3-4.4 GHz. It's really not very risky on the Haswell chips and Z87 boards. With proper cooling it shouldn't reduce the lifespan of the chip.
Another cooling system is mandatory to overclock. The stock cooler with the 4670K is terrible even at stock clock speeds. My most recent build in this thread includes my recommendation in the total price (Hyper 212 EVO). Your chip won't burn. It shuts itself down before it hits a harmful temperature. Even if you removed the cooler completely it would shut itself off before damage.
Another cooling system is mandatory to overclock. The stock cooler with the 4670K is terrible even at stock clock speeds. My most recent build in this thread includes my recommendation in the total price (Hyper 212 EVO). Your chip won't burn. It shuts itself down before it hits a harmful temperature. Even if you removed the cooler completely it would shut itself off before damage.