The loathly lady's old age is what makes her wise, a fact she establishes definitively when she reminds the knight that "thise olde folk kan muchel thing" (1010). The connection of age with the wisdom of lived experience is one we're familiar with from the Wife of Bath's Prologue. What we're not familiar with from that Prologue is the linking of age to "foulness," sexual sterility, or undesirability that occurs in "The Wife of Bath's Tale." What we need to keep in mind, however, is that much of the equation of age with ugliness is made by the knight. The fact that, in the end, the loathly (old) lady is the one who saves the knight's neck and reforms him suggests that, from the tale's perspective, old age makes one wise and useful. It does not, however, make one a suitable marriage partner for a young bachelor, which is why at tale's end, the old lady becomes a young damsel.
"The Wife of Bath's Tale" suggests that the elderly have valuable gifts to share with the young.
"The Wife of Bath's Tale" mocks the elderly through its consistent use of the age difference between the young knight and his wife as a source of humor.