There seems to be a general consensus that as long as you are cooking a product in a smoker that smoke has to be applied. If you are one of these and are getting good consistent results, good.
I have been one who uses different colors and densities of smoke depending on the product being cooked. Starting from a light blue smoke toward a heavy white smoke, the whiter the smoke the less is needed and the less forgiving it is.
Look at it this way. When filling a glass with water, whether, at a drop at a time or a steady flow, when it's full, it's full, there is no need to add more. After all, we are adding smoke for flavor not as a preservative.
Depending on the color and density of the smoke, there are products that can be satisfactorily smoked in as little as a few seconds to days.
Looking at the color and density of your smoke on the ribs, it would be my guess that a half hour to forty-five minutes would be plenty.
Related threads:
Smoke Color Chart,
New to smoking or have a new smoker? -- "How to optimize your smoke",
Understanding Smoke Management - updated 12/08/14
Tom