How to tell if a m/s box is good

I put a rebuilt one from steer n gear on my Duster.
A week or so later I noticed a drip on the floor, car had not been moved.
I called steer n gear and they said to jack the front of the car up and turn the steering wheel a couple of times lock to lock, he stated it was the grease separating in the box.

I did what he said and it has been leak free for several years now.