In our hybrid, which has just under 50,000 miles on it, the Ni-MH batteries are essentially combinations of 120 NiMH batteries about the size of D-cells set up to deliver 144 volts instead of 1.2 volts. A recycling system that would handle consumer batteries would handle these (or vice versa).
As for ~50,000 miles, I have noticed no difference in performance lately, and I would not expect one, either. The base warranty for Toyota or Honda hybrids is 80,000 miles--but in California and states that piggyback on its environmental standards, 2004 and later models have a 150,000 mile warranty.
Of course, one primary advantage of a hybrid over an EV vehicle is that even if the battery pack generates 0 volts, the car still works.
Tim Francis-Wright || <Imagine a clever .sig file here>