The fact is, with a water temperature of 160 to 165 degrees F (74 C) it takes just half an hour for all disease causing organisms to be inactivated. At 185 degrees this is cut to just a few minutes. By the time water hits its boiling point of 212 F (100 C) - plus or minus depending upon pressure or altitude - the water is safe. Even at high altitudes the time it takes for the water to reach a rolling boil and then cool means you can safely drink it.
Lacking a thermometer to measure water temperature, you only need to get your water to a rolling boil. By that point you know the water is hot enough and that the disease organisms in your water were destroyed quite some time earlier. End of story, turn off the heat. Stop wasting fuel. Let the water cool down. Your water is safe to drink!
***
Certainly good advice.