Discs heal... that's what they do. It just takes some time to re-train proprioception and let them resorb.
4 years is plenty of time.
If you've been doign proper workouts and stuff you might not even notice you even had a herniation on MRI.
Its true, im forced to workout now or I suffer with tons of pain. Like you said after 4 years most of the original pain is gone and once in a while I'm sore or if I go for my jogs/ intense physical activity.