Is it possible that some perpetual criminals actually do enjoy living in prison?

They become institutionalized, prison doesn't prepare people for the outside world and reform them, they just get punished and when someone is used to that lifestyle, they don't know anything else.

I don't know about enjoy, but surely you've heard of becoming institutionalized.

The devil you know, etc.

I'm not sure if anyone actually enjoys it, but some have been in prison so long, that's all they know and they are often unable to live on the outside.

Many have mental health issues
Quite a few are semi or totally illiterate
True crooks rarely end up inside

Yeah they become institutionalised. Some of them have a better time there than at home.

Yes, just like perpetual students never graduate.

yes.