I have been using NiMH rechargeable AA/AAA batteries in all my lights and other frequently used electric/electronic devices for quite some time.

Some of the oldest batteries (+/- 5 years old) have just stopped working. They are totally empty, and impossible to charge. When I insert them into my Varta charger, I get an error message.

Lately, some of my newer batteries have also started acting up. I can charge them all right, they seem to deliver the right current, but after a relatively short period of use, they are empty again.

Now, I wonder if these batteries have reached the end of their lifespan. Does anyone happen to know what the normal lifespan of AA/AAA NiMH batteries is? And is this only determined by the number of charge/discharge cycles, or does time/age play a role as well?