I get good results too with kens. I mix it with hikari and feed shrimp, salmon, and feed vegies here and there. I like the results. I really don't care if my fh live beyond 5 years. Call it irresponsible if you wish but to me getting emotional over fishes longevity is silly, it's a fish and is replaceable. I like the rapid growth that I get from the bulk fish farm foods. Feeding your fish expensive foods to promote longevity seems like a waste of money to me because there are so many other factors that can kill your pet besides a fatty liver.
Fish keeping is a hobby and not my life, I strive for great looking fish. There is no way you can recreate natural food selection of these fish in a closed system such as a fish tank. Some foods are better than others but the price you pay for that is weighed against the advantages. I don't see having a fish for 20 years as an advantage... Some may argue, judge, and tell others they are wrong for the way they keep fish, but it all comes down to the individual on how they want to feed, how emotional they are, their goals in life, and how much they are willing to spend on the hobby. I think it's funny how some people take fish nutrition more seriously than their own. (post not directed at anyone or critical to how one chooses to feed their pet)