Stop CNN model at high accuracy and low loss rate?
Early stopping is determined based on the validation set's results (either loss, accuracy or some other special metric).
Usually early stopping is checked every single epoch so you will need to check your validation accuracy/loss after each epoch. You don't have to print it, but if it is already calculated, there is no reason to withhold it from yourself. (you can also check validation results every x epochs if it slows your training process too much).
There are many sources that show how to use early stopping with tensorflow:


Early Stopping with TensorFlow and TFLearn

Early stopping with tf.estimator, how?

Early-stopping functionality for use with tf.estimator API.