How long does original Game Boy battery backed memory last?

I have a Nintendo Game Boy Pocket (which plays original monochrome Game Boy games and is probably not capable of playing Game Boy Advance or similar "advanced" cartridges.) At any rate it is the original Game Boy system, released in 1989 by Nintendo in America and Japan, and 1990 in Europe. This is the system I am talking about here.

I have researched a relevant question which covered much of what I was wondering about overall:

Will I definitely lose my save state while replacing the battery?

This question and its answers largely cover what to do if you really want to replace a Game Boy cartridge's battery backed memory if you have to, though the operation is risky, as you do have to keep the cartridge connected to power to pull this off, and also the battery is soldered on, so you would need a soldering iron if you really wanted to change the battery of a Game Boy cartridge (Game Pak as Nintendo called it in the day) from what I can gather.

So my question is: Just how long does this "battery backed memory" of Game Boy games last? I understand that save states on cartridges that feature this "battery backed memory" are called such because it is RAM (Random Access Memory in computing) which requires electrical power to keep its memory state. Hence, the "battery backed" part of the memory which is done in this kind of cartridge with a small battery within the cartridge, which is how these cartridges save save states of many, but not all, original (monochrome which is the kind of Game Boy I have) games for the original Game Boy. So the key question here is: Just how long do these batteries last?

I have had most of these games since 1990-1995, and I am quite amazed that the batteries backing the memory that have allowed save states to be stored on all of those cartridges has lasted as long as it has. If it lasts my entire (80+ year) life it would be incredibly sweet. But I am seeking some kind of knowledge about just how long these batteries that back original Game Boy memory last, and about when I can expect to have to replace them if I want to keep save states on those games in the mid to far future!

Solution 1:

Unfortunately, the answer seems to be "It varies":

• Old MCB1 games with the CR1616 are expected to retain data for 15 years +/- 5 years. About now, in other words.
• Old games with the CR2024 are expected to retain data for 40 years, so still no worries there.
• I'm unable to find the expected life of cartridges with a RTC, but as a matter of fact; some of them died as little as only 7 years after manufacture. Because of this, I find that they must drain more than 2uA which is more than 5 times as much as the regular cartridges. With a replacement CR2032 in place of the CR2024, I find that these will still only last about 10 years.

(Credit to Moonsweeper on the AtariAge forums for the research and electrical math)

It varies a bit depending on the batteries used (even within the same battery type, there may be some variance depending on the quality of that particular production batch of batteries), which chipset was used in the production of the cartridge, and what the battery is expected to do (the persistent clock in cartridges like Pokemon Gold/Silver/Crystal)

At this point in time, if the (original) battery is not already dead - then it is part of the second group and has a ~40 year lifespan. If we subtract time passed since manufacture (~29-24 years) we can estimate that these Gameboy cartridges still have another 10-15 years of battery life left, give or take, before they too must be replaced to retain save data.