Somewhere along the line during my travels into the internet land of the Battery Dork I ran across a few people saying that the new Li-Ion AA batteries can last something like 7 years in a low-drain device like a CO detector when the Alkaline versions only last a year. Sure, they're made for high drain devices, but when you put them in low drain situations the Li-Ion remains pretty stable and they just keep on ticking.
Or so I'm lead to believe. Currently running a real life experiment. I'll have the results in 6.5 years.
Standard Lithium Batteries have excellent cold weather performance and also have a shelf life of 10 years compared to Alkaline which is 2 or 3 years. That's why there are lithium batteries in all my "Stick it someplace and forget about it unless you really need it and then it had better work!" devices, like my glovebox flashlight.
In regards to what you said about CO detectors: Not only is what you said probably true, but you can actually buy 10-year smoke detectors. They have a non-replaceable lithium battery and are meant to be installed and forgotten. They run for 10 years and then you throw them away. They activate when snapped to the mounting plate for the first time. They can not be deactivated, unless you deactivate them permanently by pulling out a plastic pull-tab on the back. You can silence them in a non-emergency situation, like most detectors, but you can't shut them off completely. I bought smoke detectors like this at Walmart for $20 ea and installed them in my apartments.
There may be 10-year CO detectors as well, look into it.
Someone told me long ago that the 6-month battery replacement guideline on smoke and CO detectors has more to do with an alkaline's shelf life than the current draw of the unit. I believe that has a ring of truth to it.
