For the 12 " Inch Linear Actuators 225 lbs 12 Volt DC, will they operate repeatedly in the 150-200 lb. range without failure?
It depends how you defined "repeatedly". They have a duty cycle of 25% at full load and should not be operated continuously for more than 3 minutes at full load. If you are going to use the actuator at full load for 45 seconds and let it rest for 25 seconds then you could repeat this process indefinitely.