Hi my dad died of liver and bowel cancer and when he became confined to bed he would say to me every day " I wish it was all over" I can honestly say I couldn't blame him, he was an active man all his life and it was difficult  for him to be sedentary and difficult for me to watch his decline.  There's nothing you can do except be there for them and respect their wishes and listen to them. Once the syringe driver went in he slept a lot and the communication tapered off, so enjoy any chats you have while you can.