I think for AIs their bodies would be too useful to just throw away.
Instead, I suggest that instead it is their minds that have to be "killed" and a fresh AI is loaded into the valuable (and still warm) shell body.
If you want to have a setting where AI's die as much (or more) than humans, perhaps have AI's suffer old age much faster than humans and the mind of any AI inevitably becomes senile and potentially dangerous given enough time.
I suggestion for a pain-free solution for putting a AI out of it's misery would be fragmenting it's consciousness so that it loses it's sense of self and does not fight back against the incoming AI personality.
Also, there would have to be a few levels of intelligence based on the purpose of the AI and its body, so maybe include the flaw that the smartest and most powerful AI's are also those that last the least amount of time and need to be rebooted the most often.
-Edit-
I see you are quite attached to the idea of AI having rights over their own body (a noble idea), but I would then say that governments/corporations would not attach AI to valuable things like buildings or vehicles.
But if resources are so abundant that this is a non-issue, then I believe that diving into a sun, a planet with a caustic atmosphere or black hole would be an appropriate send off for a super-intelligent AI space ship.
