This is a nice example of the limitation of metaphor, and it occurs on two different logical levels. First Ratbert worries about his wisdom being derived from bad analogies (a form of metaphor). Then Dogbert responds to this worry with an analogy that implicitly compares his wisdom to wine, and then punctures it with his last observation.

Metaphor can be very useful, but it always has this inherent limitation–Is the analogy really appropriate, or is it misleading–or perhaps both? One of my favorite sayings points this out well: “The early bird gets the worm. . . . But the second mouse gets the cheese.”