What people nowadays call memory effect is a combination of two things.
One - cell aging. Batteries don't last forever. The older they get, the less capacity they have. Live with it.
Two - "voltage depression". Voltage depression is a problem with NiCd batteries and, according to some sources, also with NiMH, and it doesn't affect the battery capacity much at all. Rather, the battery voltage drops unusually quickly as it discharges. Gadgets that monitor their battery voltage therefore think the battery's flat earlier than they should. There may be lots of capacity left at the slightly depressed voltage, but the gadget doesn't know that and flashes its "low battery" warning.
Fully discharging cells cures voltage depression, but if you fully discharge a whole battery then the stronger cells in the battery will "reverse" the weaker ones. The weaker ones go flat first, and then get charged backwards by the others. This is very bad for the weaker cells, and will kill a battery pack quick smart. So don't do it.
Fancier discharging hardware lets you set a voltage to discharge to - say, 0.9 volts per cell. A NiCd or NiMH cell that's down to 0.9 volts under moderate load has practically no charge left; it's very nearly dead flat. But stopping the discharge at that point, rather than letting the pack slump down to zero volts, should save weak cells in the pack from any significant reversal. Well, unless they're so weak that the pack's toast anyway.