We finally managed to kill our Panasonic, it was still working, just the volume was not quiet loud enough for me - damn old age. We promptly replaced it with another Panasonic, which no doubt has a load of new features that we are not using. This one has standard re-chargeable AA in it, so when they die they should be easy to replace.

This is the one we got, but it can be ordered with additional handsets, and on Panasonic's site I saw a range extender available for those with huge houses. The only thing I don't like about it is that it does not mount flat to the wall, I'm not sure if that is an option any more.