Pack lifetime, NiMH vs. Lithium?

Have the OEM lithium packs been around long enough to compare pack lifetime against the OEM NiMH ones? This would be the mean (or median) time until pack failure for the two types. (Other differences may be significant but are not the point of this thread.)

I believe the 4th generation is the first where this comparison is possible. Our car is a gen2, and there was no OEM lithium option. The aftermarket lithium option was not as long lived as the OEM NiMH, but neither were most of the aftermarket NiMH, so that isn't much of a predictor for the OEM lithium.