Eneloop batteries can hold at least a charge for 10 years! There is a test on this website that shows a 10-year-old Sanyo Eneloop still having charge left after 10 years. Another discharge test can be found here: http://budgetlightforum.com/comment/1477075#comment-1477075 where the batteries in question were 12 years and 9 months old. Discharged right out of their package!
Eneloop PRO will lose a charge quicker, but still only 15% within 1 year.
Here’s the test I did with 10 year old Eneloop batteries.
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