For the lifespan of a droid, there was an episode of the Clone Wars cartoon where Anakin and Obi-Wan went to the Angels' homeworld which the Seperatists had taken over as a dumping grounds for obsolete droids, ships, etc., and the droids were mostly still operational after several years. On the other hand, some kid managed reprogram himself an entire army of droids and starfighters for kicks, so he probably recharged them at some point. However, since the regular battle droids were built using the cheapest materials available so they could built en masse at low cost, I doubt they would last any longer than the clones before deterioration set in.
I think it was the later droids that started cracking jokes, the early ones(Episode I-ish) were mostly all business, even if they were bad at it("I need to take these people to Coruscant." "TO WHERE?" "To Coruscant." "DOES NOT COMPUTE. OH WAIT, YOU'RE UNDER ARREST."). Besides, their humor was so bad they deserved to blown up anyway.
They do stuff like this in Star Wars novels all the time (I know, I'm a Sci-Fi and Fantasy Librarian). They even described sounds in space as having been manufactured by a computer inside the cockpit to make it more psycholigically acceptable to the pilot (after all, nothing will break you more than NOT being able to hear your buddy get torn apart by laser beams).
They do that in Shattered Horizon as well. Turn off your suit(or get hit with an EMP grenade) and everything goes quiet.