If I may contribute here...

Most rechargeable batteries (NiCD, NiMH, Li-Ion) need a few "very full" charges (and not quite so deep discharges) cycles to fully activate or "set up" the battery chemistry, and thereby maximize the available capacity of the battery.

Once that has occurred, you maximize battery life and capacity by conforming to the appropriate charge/discharge needs of the battery type.

"Memory Effect", which could be better described as "voltage depression" during discharge, primarily affects NiCD type batteries. It occurs when slow/partial discharges followed by recharges causes the chemistry in the battery to partially crystalize, which raises internal resistance, and shortens the discharge time before the battery voltage reaches the lower limit for the device being powered. If the partially crystalized NiCd battery is then fully discharged, then charged, after a few cycles, the internal crystalization dispates, and most of the usable battery capacity is again available.

NiMh batteries are so much less suceptable to voltage depression that even when it has occured, the loss in capacity may not be noticed by the user (maybe only 5% capacity loss).

For most NiCd and NiMH batteries, the primary killer is poorly designed battery chargers. Many chargers continue to push substantial power into the battery after it has become fully charged. This continued overcharging causes chemical degradation of the battery chemistry, and is not reversable once the damage has been done. Frequent overcharging (which can occur even if the batteries don't feel "hot" in the charger) will substantially shorten the battery life and reduce the effective capacity.

If you are getting significantly reduced capacity and short lifespans from NiCd or NiMH batteries (even if you are recharging them before they are empty), you should suspect the charger is overcharging the batteries. If a few full discharge, then recharge cycles don't bring them back to life, then either the batteries are truely worn out, or the charger has done them in prematurely.

Li-ion batteries (which have impressive power density and light weight) are so sensitive to charge and discharge requirements that they are always managed by a very smart power management circuit, which relieves the user of concerns regarding the best charge/discharge strategy.

For Li-Ion powered devices, just use the device, recharge it when you want, and don't worry about the battery (other than _fully_ charging, and significantly discharging, the first few times to fully activate the battery chemistry.)