I like Ray's rule, although I've bent it myself on many occasions. (I'm talking like 2 big corals at once - or a bunch of little frags.) As the tank is more and more established, you can do a lot more. When we were first getting started, 1 coral per month was a good rate for us. (Not to mention was easier on the checkbook!)
I wouldn't apply it to tank upgrades, when you have to get the old tank torn down. Reiple, if the new tank is using old rock and a small amount of new, you could probably transfer the corals without problem.
Oh, and I consider "cleanup crews" one entity. Adding a dozen hermits or 3 dozen snails has never caused me problem. (I think Spanky adds hundreds at a time...

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Danielle