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1- The narrow band O2 sensor produces the voltage directly from a zirconium dioxide cell. It is the source of the 0-1V signal. A signal of .250V means nothing more to the life of the sensor than a signal of .500V or .750V.

2- The operating range of a narrow band O2 sensor produces a calibrated 0-1V output over air fuel ranges of 17.0:1 to 12.5:1.

3- The output characteristics of narrow band O2 sensors are most accurate in the 14.0:1 to 15.0:1 range. The O2 IED happens to be working at 14.2:1, which happens to be in the range where NBO2 sensor output is quite linear. While the response curve of nbo2 sensors is more abrupt over 800mV, it is still within the design limits of the O2 sensor.

4- The OEM fuel map in the Harley always has the bike running at 12.0:1 just after engine startup. There are significant portions of the OEM HD fuel maps and the HD Stage 1/2 upgrades that put open loop AFRs at 12.5:1 AFR.

5- If you use SERT to tune the Bias Tables in the HD ECM, you can set the bias values to 792, which happens to be .792V or a value higher than the O2 IED artificially alters the bias table value to. So HD has obviously determined that higher voltages at the O2 sensor are not hurting it. For those who do not know what the Bias voltage means, that is the voltage that the ECM looks for to determine rich/lean values coming from the O2 sensor.

6- In the latest releases of HD ECM code, the engine goes through several stages of heat management. As part of the overheating code, the engine will richen the fuel mixture to 12.0:1. All this is explained in the latest Manual for PRO SERT.

7- Riders that have pulled their PowerCommander and TFI's that use O2 eliminators off their 07/08 (including 06 Dyna's) bikes, then reconnected the orignal O2 sensors have reported no ill effects from the engine and are not reporting ECM codes. Considering the number of riders/shops that typically set idle/low RPM fuel maps much richer than required (11.5 to 12.5:1), you would think that this group of riders would report instant failure of their O2 sensors and error codes appearing when they changed equipment.

Don't take my word for it. Below is an engineering data sheet for narrow band O2 sensors. Ask the "nay sayers" to find one word about a too much voltage output hurting the life of the narrow band sensor or too rich a mixture decreasing life. Ask them to find an "engineering or automotive study" that shows the output of the zirconium dioxide cell degrades faster with fuel mixtures falling into the operating range of the o2 sensor. Ask them to find a well know and trusted performance Harley mechanic to prove that running an O2 sensor is going to decrease the life of the sensor. The best they will probably do is mention a "friend of a friend" that had a problem with an O2 sensor after doing some work on the bike. And I'd be willing to bet I could explain the premature failures of any O2 sensor based on my comments below.

Things that I do know will hurt the life of any O2 sensor are:
the use of leaded gasoline (or additives),
operating temperatures well over 1400 degrees,
very small amounts of silicone sealers getting into the combustions chamber or exhaust stream (which is why you see automotive stores selling O2 sensor friendly gasket sealers)
In the HD world, the use of leaded fuels/additives is common and the use of silcon sealers that are not O2 sensor safe are both fairly common. So any premature failures are most likely due to one of these.