Many years...
We've been using the Science Plan foods for our dogs ffor many years. We have one dog who has been on them for over 15 years! Jess, our choc lab, has been on it since being diagnosed with elbow displasia at 18months. She'll be 18 at New year... We unfortunately lost another of our our labs this time last year at nearly 17.
I can confidently say that it keeps them in good condition and is easy to regulate their weight on 2 feeds per day (with appropriate exercise!).