I've got an FEH with a big ol' NiMH battery that's about 2.5 years old and a EV drivetrain that has the guts of a Prius Type I. Since older Prius batteries are similar to mine, what are users experience with older, high-mileage batteries? Have drivers experienced a decline is performance/efficiency that's noticeable to the driver? (that is, without a multi-meter and bench experiments!)