What is the age that they start to leak? I have never seen this documented anywhere.

I know Foreflow and I disagree on this but what is the age that they start to leak? I personally don't believe there is any age factor involved, that would cause leakage issues, and their life expectancy in storage is decades. On the very rare cases that these do leak, its far more likely they were subjected to an inadequate storage environment with large temperature swings, dampness, or excessive temperatures.

The memory standby current is 10uA (0.000010A). Energizer AA Lithium batteries are rated at 2.8AH each, since they are in series the entire bank will proved roughly 5V for 2.8AH, this calculates out to battery depletion in approx 100 years. With this extremely low RAM standby current draw, the expected shelf life of the batteries is much lower (5x) than it would take to deplete them; however, the RTC likely draws more power in operation than the RAM does, this circuit is an unknown load on the batteries.