There is no exact answer for how long your system should run during each cycle. The average air conditioner is sized to remove the heat from your home as fast as it comes in, on a 100° day. Therefore, ideally, on a 100° day the system should be able to keep up with the incoming heat, but not gain on it and be able to turn off. The cooler it is below 100°, the more the system will cycle on and off.