I watch my batteries pretty close, by that I mean, I mark everyone of them as to when they were first charged and what the present mAh rating is.
I have 60 rechargeable batteries; AAA, AA, 9v, D and 18650's and what really keeps them in tip top condition is the chargers!
I have some batteries now, that after 3 1/2 yrs, have dropped from 2700 mAh down to 2000 mAh. I can check them by using the charger made by MAHA - model C9000 WizardOne.
This charger will charge the batteries several different ways and show what the mAh is after the charge.
The low discharge batteries are excellent for holding a long charge when not being used. But I have also found out the Sanyo 2700 mAh batteries to hold a good charge (80%) after 9 mo's or more. But these batteries were first charge with the "break-in" mode using the above mention C9000 charger and they were also "new".
A good charger is a must, for the longevity of your batteries!