After eight months from a full charge, an old NP-BX1 lithium battery has come to this:

The astable still ticks along at 1.4 seconds per blink, but the green LED barely lights up from a 2.1 V battery:

A pulse of 12 mV across the 100 Ω resistor puts the LED current at a mere 120 µA: no wonder the poor thing wasn’t visible in ordinary room light.
Another full charge restored its vigor for another couple of seasons.
Only 8 months on a charge! Nothing lasts!
And it was the Genuine OEM Sony battery, too! [grin]
I was hoping for a year. Maybe a pair of fresh alkalines will get there?