Not sure if this is the right place to discuss and can't find an exact answer in the other discussions.
My smoke detectors were manufactured in 2009 so its time to replace. They are hardwired and linked together which I am planning on keeping so the battery is just a backup.
My question is around the backup battery, does a normal backup battery last longer in these units since they are not supplying power directly such that I could use a 9V lithium for a few years at a time? I'm aware of the discharge curve of these batteries such that once they reach end of life they need to be replaced immediately but I see the risk as relatively low since it is a backup power source.
I know the recommendation is for replacement yearly in both wired and battery powered units, but these sealed units have a supposed 10 year life without needing replacement which I would assume is similar to a normal 9v lithium. Some people say they fail after only a few years so I was thinking by purchasing the models with battery compartments I could easily swap the batteries if need if they fail early but get the same benefit of extended life with lithiums? Does anyone else do the same and how long are they getting out of the batteries?