wrandyr,
NMH deteriorate slowly, internal resistance grows as capacity decreases.
Deep discharges, high temperature, charging in extreme temperatures, all this shortens life of NMH.
Remember EPLUS 36V needs 30 cells in series and such pack is as good as the weakest cell in the string of 30.
EMS , manufacturer of EPLUS used the best NMH available - GoldenPeak brand, but still chemistry is chemistry.
From my last conversation with Rick Ruggiero who still services EPLUS /I am afraid not for much longer/ he wants $1,000 for new front hub and
$700-$800 for used ones.