Now, I really like that song and I always kind of regret it when it's over and wish that it had been a little longer. And then I realized that this is another valuable lesson for writers of filk (or music in general for that matter).
They had said everything that they needed to say. They had said it in an amusing and witty way. And then they had stopped, leaving the audience wanting more instead of manufacturing more verses of lower quality.
Brevity. What a concept!