[tinco]

If you assume a normal cell phone user charges his phone at night, and it will work the whole day, it means around 8 years of use.

If you calculate from lithium ion, based on my own experience with my phone and my macbook, a lithium ion battery crosses over into the less acceptable performance after 4-5 years.

If the degradation curves can be compared that would mean you could expect 12-15 years from these batteries. Pretty impressive!