Longevity of O2 Sensor ?

My 98 XJ has passed SMOG checks every year with flying colors for the
past 10 years....
Figure after 10 years of use; the sensitivity of the O2 sensor was not
near as responsive as when it was NEW....
Today I decided that it was time to replace the sensor before the next
SMOG check.
With the change of the O2 sensor.... I am hoping to see a little
difference in gas mileage !!!!!
Did some price shopping... online and in Escondido.... I purchased a
Bosch 13100 from Kragen; since they would beat ANY competitors price
by 10%. Total price with tax was $56.

Just curious how long you have used O2 sensors; before
replacing...

They usually have a 100 thousand mile replacement interval.

Did you disconnect the battery after replacing the sensor?

YES....
Disconnected the battery for several minutes....
Waiting to see IF there are any differences in gas mileage or performance....