Originally Posted by Solicitous
How are you coming to a 3 year life of the Kobo? Given the batteries in most consumer electronics are calculated at between 300-500 charge cycles, IF you charge the Kobo once per week (worst case scenario), that equals 50 times a year. At worst you'd be looking at 6 years before the battery starts to decade (under ideal conditions).
If you take a look at the wiki here on the forums you'll see pics of a Kobo dismantled, so if in as you are saying 3 years the battery needs replacing, you should be able to dismantle the Kobo and replace the battery with relative ease. Provided the same voltage (and at least the same mah to keep good uptime between charges) battery is used you'd be fine.
Then again as others have pointed out with changes in technology etc, it is more probable you would have replaced it with a newer model because you want to rather than the Kobo is all worn out.
Ultimately if you are worried about battery replacement you could look at the Eco Reader, it uses a standard Nokia mobile battery, which is user replaceable.
I am using 3 years as the maximum life of these batteries, based on technical web sites devoted to batteries. They seem to have a useful life regardless of the number of charge cycles. They start to die from the date of manufacture whether used or not.
While many people will want to get newer stuff, I want to get more useful life out of what I have, and there just don't seem to be any real advances coming for essentially, that which is just one page at a time. I don't play with my eReader, I read it. I was also amazed that they told me that they assume I will throw it away when the battery wears out. It just struck me as a poor choice of words.
In any case, I found another nook that I can softroot, so I am fine, replaceable battery and all.