How to calculate the number of cycles my linear actuators can run
keep the input 12 volt constant. Use a 12volts - 60 watts DC adapter. The speed is provided in the manual. It's 20 mm/sec. I've used these many times. Speed doesn't vary if the input voltage is constant. But use feedback. The current will drop as soon as it reaches maximum or minimum length. You will hear a sound as soon as it reaches the maximum or minimum position. It's due to the auto shut down process of the motor. And so current will drop drastically. 

If you use a battery, use a buck-boost regulator.