I'm a pretty firm believer that the customer should decide when to replace a device, not the vendor (or engineers) so their attitude over batteries is disappointing to say the least. At least within reason. By that I mean that 20 years is probably unreasonably long, yet 3 years is unreasonably short.

Now I suppose that it doesn't have to be the vendor that supplies the replacement components, but it would be nice if they did. That's especially true for batteries that have a short lifespan, and because rechargable batteries seems to be a bit of a black art. (I'm a physicist damn it, not a chemical engineer. I would hate to see how confusing it is for someone who pursued interests outside of the sciences.)