NiMH Battery Indefinite Charging
At first, NiMH cells did not have a catalyst to recombine H2 and O2 liberated during even mild overcharging, and seals would rupture from gas pressure. Most NiMH now contain a catalyst to reunite the gases, releasing heat and water (as do catalytic lighters).
As long as the charge rate is low (less than C/40... I use C/100), a NiMH cell with catalyst can be left on maintenance charging indefinitely, so in that case, current limiting is better than voltage limiting. Current limiting also protects a battery from further damage should a cell short: a 14 V battery with one dead cell could not charge above 13 V, but would receive full current from a voltage-limited-only charger.