I7 2600k overclocking

i am new to this field(overclocking). from what i have read, i think the intel have unlocked the k series ie multiplier can be adjusted. But at the same time won't the warranty be broken if overclocking is done.

also is a external cooler essential for oc 2600k(multiplier change to 40 keeping the voltage and bclk at stock (100mhz)) if using a stock cooler is enough then what would be the max temp. or is it the other way ie does multiplier change, bring about voltage change automatically. need explanation guys.

apart from this is it better not to overclock if you are planning to use the system for a period of say 5yrs.(lifespan consideration) need help dudes.

gaming would be the most cpu stressing factor in my case and do gaming requires a higher clock, ie wont 3.8ghz(with turbo) be enough with today's games(with a decent gpu). also is turbo boost by default active or should we manually switch it on(motherboard does support turbo boost).

whats your opinion...

generally Intel supplies a fairly solid performing fan and heatsink with their processors, i have heard extremely good things about the 2600k stock cooler, most people are getting 4.5-4.8 ghz on the stock cooler without adjusting voltage too much, leaving the processor at a very moderate temperature range, the i7 2600K is fully unlocked and overclockable to the extreme but you will need a P67 or Z68 chipset in order to access that overclocking potential

As long as you dont exceed 60 to 65 C very often then your cpu should last quite awhile and thats achievable past 4ghz