This is a constant I'm afraid.  When speaking I like to have realistic examples, because I hate seeing over simplified examples that don't add up to a real application - leaving you with only half the picture.  There is a balance though, you have to cover the main topic and too much "side code" can confuse someone who may have never seen such code before.  My approach (when speaking) has been to build an application people can download, then focus only on the parts relevant to topic at hand.  Never had any feedback good or bad from anyone who downloaded the application if that helps or not.