Originally Posted By: Arney
Perhaps the 6-month rule came about at a time when batteries were less reliable, and 6-month replacements made more sense? I've never seen a leaking 9V, and with the availability of lithium 9V cells now, you could go many years without changing those puppies.

I've always wondered how necessary the 6-month replacement rule is.

It reminds me of vehicle maintenance suggestions; cars all used to say the oil had to be changed every 3 months or 5,000 km. I always thought that was excessive, and newer vehicles with oil life monitors seem to be proving me right; according to GM's info on cars with their oil life monitoring system, "[m]ost GM vehicles average 13,500 km between oil changes." That's quite a difference.

It makes me wonder if we are being wasteful in changing all those batteries on a 6 month schedule (although searching around I see quite a few organizations recommending annual battery changes now - example).

As a side note, some manufacturers are now selling 10 year smoke detector models with lithium batteries installed; they say the life of the unit is the life of the battery so you just replace the whole unit at the end of 10 years.
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Victory awaits him who has everything in order — luck, people call it. Defeat is certain for him who has neglected to take the necessary precautions in time; this is called bad luck. Roald Amundsen