<p>This is not necessarily abusing the SE system when you provide extended answers, as long as they can be justified other than by pure digressions. Answering a related subject in passing might also be a good idea, if you feel that this would be useful for the OP and future readers. (In this particular case, the number of upvotes you got suggests you were not too far off base :) </p>

<p>Once you're done with the take-away message, it is fairly easy to add further considerations in your post: You can highlight your main points in the first part, and then append side notes or related topics in the remaining part. Or as @mbq said, you can build your answer incrementally. </p>

<p>Finally, some facts I have noticed with time: </p>

<ul>
<li>Good answers often go beyond what look like seemingly simple questions (that's why it is also important to comment early on new question, i.e. to help clarify what the OP is <em>really</em> looking for).</li>
<li>Good answers often increase interest in the issues raised by the OP.</li>
</ul>
