There was a documentary on this subject a while back and it followed families who were considering and those who went through this process. It seemed a tragedy that they had to travel to a foreign country for them to be granted their wishes.
Both my mother in law and mother suffered in their latter days, and although neither of them had expressed a wish for assisted suicide, both of them did ask for help towards the end.
We had been told by doctors that the mother in law had hours to live and she lived for another two weeks crying out in pain. We would not have allowed an animal to suffer in the manner she did.
My own mother didn't suffer as much but was crying out in pain in her latter days. Medical staff knew she wasn't going to recover but allowed her to go on in pain, why?