Yes, and it won't return . . so just drive it and
at those Rochester winters!
If you find (or acquire) a scanner such as the AST Retreiver (or equivalent), then you can read the S/A numbers directly and see how it's trending.
When mine tripped the limits at 0.85 (limits are +/- 15%), I replaced the eprom and it continued to trend downward. The new eprom has limits of +/- 32%, meaning it won't trip again until 0.68 is exceeded. That probably will never happen.
If I remember correctly it got to about 0.83 and I replaced the MAF and O2 sensor (b/c I got them almost new very little $$). The S/A was reset and after checking every month or two, the S/A was just on the "good" size reading 0.88. It has continued to rise to it's present value of 0.92 or so. And that's where it stayed.
Steve Brotherton (stevebfl) tried some experiments placing a 600 ohm resistor in the line which immediately changes the "precentage" and it raised the S/A to the "good" side of 0.85. He may comment if he read this.
But this is a nice fix and if you feel "rich" (or get a MAF and O2 cheaply), you might try replacing them. With new parts, it's a very expensive "fix" if it even works.