The boiling times are relative. The answer should really be "it depends". It depends on altitude for one. Water boils at 200F at 6,000ft elevation. It boils at an even lower temp as you climb higher. You would need to boil longer vs. shorter at higher altitudes to kill off the nasties.
True, altitude does indeed change the boiling point of water, but I am seeing evidence that water heated to significantly below the boiling point will adequate disinfect same. Let me quote one of my favorite authorities - James A. Wilkerson, MD, Medicine for Mountaineering, 6th ed. , p. 65 - "To eliminate Cryptosporidia, CDC and the EPA recommend boiling water for a full minute (three minutes above 6500 ft or 2000 m because water boils at a lower temperature at higher altitude).
[/b] [emphasis added]However,simply bringing water to a boil is just as effective.[b](Milk is pasteurized, which eliminates most organisms, by heating it to only 160 [degrees] for twenty to thirty minutes. Many cookbooks also recommend cooking meat until the internal thermometer reaches 160. See a trend here? If my memory serves me right, 160 F is about the temperature of boiling water on the summit of Everest.
I typically will either just drink the raw water, or bring it to a rolling boil. I have a filter, which I rarely drag around with me, and somewhere in my junk I have various potions and pills to drop into questionable sources. But if I am really concerned about the quality of the water, it's "boil, baby, boil."