Green led on/off depends from design of battery charger. In many chargers green led turn on when charging process is over. To check your battery capacity you can do few cycles of it, I mean complete charge and discharge few times.
This NiMh wide consumer batteries have life of 3-4 years used or not used or 1000-1500 cycles. If they working then good.
NiMH and Nicad batteries, start to lose power when stored for only a few days at room temperature. But they will retain a 90% charge for several months if you keep them in the freezer after they are fully charged. If you do decide to store your charged NiMH cells in the freezer or refrigerator, make sure you keep them in tightly sealed bags so they stay dry. And you should also let them return to room temperature before using them. If batteries dont show some life, then you can try to start some chemical process, try to freeze them several times.