Can ABS sensor go bad only for a while?
 

I had an ABS light on for a year. In the mean time I went to the Mercedes dealer to ask for estimate and to determine the problem. After one hour and $85 mechanic told me that one of the ABS sensors is bad (did not want to tell me which one do) and everything will cost me around $289. Told him that I will be back but I never did. Week ago I was changing oil at my local mechanic shop. I told him about the sensor problem while the car was in the air. He poked the rubber or plastic conector on the top of the sensor and since than I got ABS back. The light is gone and today on the little snow we got in Chicago I had a chance to try it. Works like the old days, great! My question is:

Will this fix stay for good or should I be expecting for the problem to come back. Can the sensor work On and Off?

1988 300CE