Hi NoGround, I believe that SundaysChild gives some valuable advice. Each family and each addict is slightly different.
Frankly, I don't care for detailed rules for Trustees, because it can backfire. The link that you provided recommended that the Trustee doesn't distribute unless the beneficiary is two years clean and can prove it with drug tests. Well, that sounds reasonable, but after a bit of experience, my opinion is that an addict could game that system pretty easily and then use the trust distribution language to force the Trustee to distribute. All the while the Trustee and the beneficiary's family may realize that the beneficiary is still using. How many times have members here had that gut feeling that their RA was no longer recovering, but couldn't prove it with drug tests? I don't want to turn the Trustees into the drug police.
If you are fortunate enough to know someone who will make a good trustee, I find the best solution is to pick good Trustees, make sure that they understand the problem and give them full power to use their best judgment.
Another method and one I just adopted is that I created a trust and restricted all distributions until the beneficiary turns 55 years old. I figure if the child remains an addict or relapses, she will not live to see 55 and then the trust corpus will pass to her siblings, if she survives, she will have a nice retirement. I also told her about this provision in my will and warned her that I hope she remains clean and when I feel more certain about her future, I will change my will. However, presently she just better hope that I don't die before she has developed a good track record or she is going to be without funds for a very long time.
Finally, I really dislike disinheriting children. There are times when it is appropriate, but those are few. Its like a final slap from the grave and the child has no ability to respond. If a parent does take this action, I recommend a small bequest like a family memento that has no financial value and was important to the child. I also recommend preparing a private letter to the child listing your reasons in a non-angry manner and, if at all possible, assuring the child that he or she was loved.
Just my thoughts.