Any harmful consequences in deferring the renewal of a defective oxygen sensor?

If the cost is an issue, this web page http://hsb.baylor.edu/html/easley/autofaqs/o2sensor.htm
describes the procedure for putting in a generic equivalent. Mine is due to expire in about 5K miles,at which time I will put in the generic model. I can post my results, but if you do it, let me know how it works, please.

O2 sensor problems
 

I just had my O2 sensor replaced in order to have the car pass the required emissions inspection in the Atlanta area so that I could renew the tag. The defective sensor was causing the engine to run very rich. So you can have emissions and other problems as a result of a bad sensor.

Actually, this was more of an academic question, on a friend's behalf. His "Check Engine" light illuminated at 55K miles; dealer service at 61K miles indicated that the oxygen sensor was bad. Other than the warning light, the vehicle is asymptomatic (no change in fuel economy or performance) and his state has no emissions inspection, so he's felt no pressure to renew the sensor.

As for theoretical consequences, decreased fuel economy and increased pollutants come to mind; additionally, extended running in a full rich condition would eventually damage the catalytic converters. Any other harmful effects related to a failed sensor?

In some cases this could result in plugged $$$$$$$$Catalytic Converter$$$$$$$$$$.

Have a great day,