What factors erode trademark value?

In addition to registration, valuation analysts look at three significant factors that can quickly erode trademark value:

Is the trademark in everyday use to represent the product class (is it generic or becoming generic)?  “Kleenex” is used to represent tissues, for example.  Xerox fought hard to distinguish between “making copies” and “Xeroxing.”

Has the mark been abandoned? Is the mark used in commerce and is it used to represent the product or service for which it was registered?

Most importantly, does the owner of the mark have the willingness and wherewithal to prosecute infringers?