I think some folks have the wrong impression of what a resistor does, it “resists” or “slows down” the flow of electrons in a conductive circuit. A fully charged battery has a capacity, essentially a quantity of electrons that want to move from the negative end into the positive end. An atomizer coil has resistance and will pass current (rate of electron flow) based upon the voltage applied to it.
When a resistor is connected in series, the value of it is added to the resistance of the coil. The total resistance in the circuit is increased thereby slowing the battery’s rate of discharge. Your battery will last longer but the atty will run cooler due to decreased current flow. It is the rate or speed of electrons moving through the coil that causes the heating due to friction.
Think of it like a tank of water with a spigot at the bottom. The further open the spigot, the less resistance to flow and the faster it will empty out. Voltage is a measure of electron pressure much like fluid pressure. Higher pressure (voltage) means higher flow rate through same size restriction whether it is a spigot, atty coil, or electrical resistor.
Since the voltage is divided between the resistor and the coil, varying the size of the resistor varies the amount of voltage remaining for the atty, too much voltage and it burns out, too little and it runs too cold. A high voltage (HV) atty has a higher resistance to keep current flow to a safe level.
Battery life will vary according to the devices overall current flow and duration of operation. If you are using a manual switch and are used to vaping at 6 volts; adding a resistor into the circuit for 5 volts may result in longer duration or more frequent switch activation thus a similar battery drain.