How much would my battery last in controlling a servo

Hi. I wanted to know a rough estimation of how much would my battery of 7.4 v and 750 mah last in powering a tower pro mg995 servo.
The specifications of servo are:
Weight: 55g
Dimension: 40.7×19.7×42.9mm
Stall torque: 9.4kg/cm (4.8v); 11kg/cm (6v)
Operating speed: 0.20sec/60degree (4.8v); 0.16sec/60degree (6.0v)
Operating voltage: 4.8~ 6.6v
Gear Type: Metal gear
Temperature range: 0- 55deg
Dead band width: 1us
servo wire length: 32cm
Current draw at idle 10MA
No load operating current draw 170MA
Stall current draw 1200MA

Also would it be safe to use 7.4v battery bcoz itz specification says 4.8 to 6.6v. I would be using arduino to control. However arduino will be powered by another supply.

Do not use it above the rated voltage .
How long it lasts depends on how often it's on ( and off) and what sort of load it is driving .

That sounds like 2 cell lipo battery and fully charged it has over 8V not just the nominal 7.4V. I wouldn't try to power a standard 4.8-6V servo with that. You need a different battery or a 5V or 6V BEC/step down regulator.

How long any battery will last depends on how much you use the servo and what load it has on it. Heavy load and/or frequent use = short battery life.

Steve

Can i use resistors to drop the volatge to around 6v.? Also i will be using the servo for like 5 times in 1 minute

Actually i am using two power supplies. One power supply of 8v is connected to l298n motor driver which also powers the arduino using vin pin. I tried using the servo directlybfrom arduino however the Bluetooth stops working whenever servo is powered from arduino. Also i am using using servo timer 2 library bcoz timer 1 is used by tmrpcm library. So i used a separate power supply to the servo using a power bank which gave 5v. And servo and Bluetooth were working properly. However i do not have the space to keep the powerbank. So i thought of using 2 3.7v batteries to power the servo. I am concerned about the capacity of battery. Will 750 mah be enough? I will be using it in exhibition which will be for about 3 to 4 hours. The servo will be used for approximately 5 times in 1 minute. So please help me

You could use a 5V step down converter from your original 8V power supply. Something like http://www.ebay.com/itm/Buck-Converter-US-Seller-Mini-360-4-75-23V-Input-1-17V-Output-Step-Down-/272582448657

No need for a separate battery and no damage to the servo.

Steve