Funny, I was just talking about them today. Twice I had them crap out in less than a year and lost my settings. So maybe test them every 6 months and make sure one is running low. That's what happened to me, the other 2 batteries were still fine.

I thought 10 years was the life expectancy. I'm at year 5 or 6 right now on probably 40 of my games with no issues.

I only had one game that kept killing regular batteries and even lithiums too. Even changing the blocking diodes didn't help so that game got NVRAM.

Check them with a voltmeter. Mine are going on three years and holding charge well.

I love the Energizer Lithiums. But it seems like they do have some kind of QC issue, or maybe it's just inherent in the technology, because something like 1 in 5 batteries will just crap out, long before its siblings do. When it happens, it tests at 0v and of course means you lose power.

On the bright side, I've never seen them leak, and they do have higher capacity than alkalines.

Unfortunately, the "battery completely failed" scenario seems completely random. If it were me, I'd just write down any settings I changed from defaults (assuming I didn't think I could remember them...I don't usually change much personally, and what I do change follows a familiar pattern, so I don't usually need notes), and replace the batteries when they wear out, whether prematurely or just from depletion.

I also keep a box of the partially-depleted ones (the ones that had a sibling crap out early). These seem to be the "good" ones (i.e. won't crap out early) and generally are still testing at 1.7v or higher, so when I need a fresh set of batteries, I just find a group that test around the same (within a few hundredths of a volt of each other) and put them in together.

You could go check the voltage periodically to try to catch a battery before it fails completely; I've had batteries fail without appearing to be near death, but it's worth a try. You'll at least catch the obvious ones.

I tell my customers to replace them every five years, but they'll easily last ten years and longer. Keep in mind that different games will not hold memory at different voltages. Regular AA batteries typically read about 1.6 volts when new. Lithiums read about 1.8. take them out every few years (with game powered on to save settings) and test them. If they read 1.2 volts or lower, replace them. Over 1.2 volts, you're good for at least another year. Modern games have blocking diodes, to prevent non-rechargeable batteries from receiving a charge. If your lithium batteries are lasting less than a year, your blocking diode is likely bad.