OK, curiousity has engulfed me and I tested one of my 9V NI-MH battery.
Battery type: 8.4V @ 160 mA-Hr rated
Brand: Chicago Electric Power Systems (green label)
This is one of the cheapies sold by harbor Freight tools,it's made in China.
TEST METHOD: Attach a 62 Ohm resistor, measure terminal voltage during discharge. At 8.4V, that's a load current of 136 mA. It will be a bit higher or lower as the battery starts at about 9.8V and discharges.
RESULTS:
The battery voltage had it's "flat area" between about 8.0V and 8.2V (stayed there the longest time). The discharge current in this area is about 130 mA ballpark which is 80% of "C" rate.
The battery dropped to just under 8.00V at time marker of 50 minutes.
The battery dropped to just under 7.7V at 60 minutes. That is 1.1V/cell and the typical "end point" for discharge.
I discharged it down to 7.0V (which is 1.0V/cell) and that only increased usage by eight minutes, ie out to 68 minutes total.
CONCLUSION:
I was shocked. If this is a 160mA-hr cell as said on the label, I was discharging it at around 80% of C rate. It delivered about 130mA-hr of capacity when discharged the full 60 minutes down to 7.7V. This means it only lost 20% from the label's rated capacity even though it was discharged at 0.8C. Pretty impressive.