That would still be too good for them.
In 20 years or so....someone MAY stick a needle in them and let them humanely die. 
This is on topic, please bare with me.
Watching a silly program about ghost hunting a 17 th. century prison being investigated,
Quite an eye opener, those folks sure knew how to change a person around right smartly.
Worse punishment for the animals was to be given 40 years or so in solitary. When found guilty the prisoner was allowed one last look at their family and led away as he was not allowed any kind of communication with them, for any reason at any time.
He was placed in a special cell that made the presence of anyone else impossible to see hear or feel.
The guards wore face masks so prisoner could not get an accidental peek of a human face. IF he had to be moved ,he wore a hood to block out all living creatures.
When food was brought to their cells they had to eat it by hand as NO reflective surfaces allowed in cells. The prisoner was not allowed to even see their own face.
No one could speak to him ,guards or medical personal, Not even a rat or spider was allowed to visit him.
In all reality they took from him the things that his victims could not have, their family, the sound of a human voice, the sight of another humans face.
Cruel and inhumane---NO WAY. This is a way of telling miss behaved Big Boys to go to their room.
The prisoners family know they will never see him again, same as if he were hung. ---Yet they also know he is alive, healthy, being fed 3 meals, has a soft bed and toilet facility's.
When the prisoner finishes doing time, gets out, if he has any living family left, they will wish he had been hung in the first place.