I own several Citizen Eco-drive watches and all of the manuals state that the secondary battery will "last a lifetime". That suggests around 70 years.
However, information I've seen from anywhere else (like here) about secondary rechargeable batteries for watches suggests that the batteries usually last anywhere from approximately 10-25 years. So, is Citizen full of it, or do they have some special custom battery exclusive to Citizen Eco-drive watches that indeed lasts a lifetime?
It's also suggested that the cost of the secondary batteries is about $40. Add shipping (about $15 insured) and the labor charge ($100), and you're looking at rather ridiculous cost if your original purchase price was $200 or less.
So, naturally it's curious to think about what it takes to do the battery change yourself. Certainly this should be possible, if you have the right tools and know what you're doing... has any watch enthusiast here done this? If you could obtain the tools, know-how, and the right preparations for doing it for about the cost of the first battery replacement, then it would certainly be an economical thing to do if you've got more than one Eco-drive watch and you're mechanically inclined...