Is changing content often good from a search perspective? This question is discussed at WebmasterWorld and a lot of good information is dispensed.
First of all, "changing" content should be considered carefully. It could potentially hurt your rankings, according to Tedster:
If a url depends significantly on on-page factors for its ranking on a given search, then changing that content can even undermine those rankings.
It's important to acknowledge that changing content is not a good thing, necessarily. Instead, you should *add* content.
Don't change your page too much. Instead, focus on building other pages.
If you change your page from just "trophy" to grab things like "trophies" and "trofies" (for people who can't spell) you divide all the focus of the page between those different iterations. You are dividing up the amount of emphasis you put on any one of the word sets. Themeing really comes into play. If you are worried about ranking for different variations of a phrase, create additional pages of content / links for those different variations. Sure it's a pain, but it's a solid tactic.
That's some really good advice. The more content, the more loved you are. That's how it typically works.
Forum discussion continues at WebmasterWorld.