Hi Neil and Russ,
Many people have had experiences similar to both of you.
For some, like me, the noni just continues to bring amazing results, year after year. I don't think it can ever stop being good for you.
For others, the results seem to be less noticeable over time. What I have noticed is that where the results seem to be less dramatic is in people who suffer from chronic illnesses. My next-door neighbour (that's Canadian for neighbor!) is a good example. When the noni was needed in greater and greater amounts to keep her going, I gave her a bottle of goji juice to try, and the results were amazing. Her health improved very dramatically, to the point, in fact, where her symptoms were virtually gone (she has fibromyalgia).
Now, bear with me - this get's even more interesting - after a while, my dear neighbour found that she needed to drink more and more goji to keep her health going, and it was getting pretty expensive. I had recently discovered a relatively inexpensive source of noni juice that rates very high in scientific studies when compared with the well known brands, so I told her about it, rather than selling it to her from my source. I suggested that she try it again, just to see what would happen.
Well, the noni juice is working, once again, is half the price of the famous one, and her health is right back to where she's feeling great, again.
So, it seems that we simply must listen to our bodies. If something works, we should stick with it. If it stops working, we should try something new. And later still, we might just find, as my neighbour found, that you can go back to what used to work with great results.
One further thing I would like to add is the fact that there are still plants being "discovered" that have been known about for centuries by indigenous peoples that have amazing health supporting and/or healing properties. A great example is the plant combination that my wife's grandfather has used for most of his life, which his northern BC and Alaska ancestors have used for centuries. I have known Grandpa for nearly thirty years and have never seen him sick. He's now 98, still getting around just dandy and still very much has his wits and sense of humour about him (Grandpa and Gran just came down from Prince Rupert for a visit.) You can't even BUY the products he has used all his life!
God bless,
Dave