The latter role he would use to again target children by working at a second and third cinema in the 1990s.
Crown prosecutor Tiffany Cooper successfully argued for preventive detention at his sentencing.
"There is a real concern about the ongoing safety of the community," she said.
The Court of Appeal gave him a warning in 1997, when a preventive detention sentence he was serving for indecent assault was quashed – a "final" warning, she said.
"We still find ourselves here in 2020."
In opposition, defence lawyer Jonathan Hudson had said a long finite prison term, with the possibility of an extended supervision order upon release, would be adequate to protect the public.
Hudson also noted Morris was 67 and would be subject to the Child Sex Offender Register.
Justice Downs said he believed Morris continued to pose a risk of re-offending despite his age.
The judge also said he believed the Court of Appeal would not have quashed the 1997 preventive detention sentence - replacing it with a six-year prison term - had it known about all of the offending to that point.
"You are at best ambivalent about what you have done," Justice Downs said before passing the sentence.
"You describe shame but you did not plead guilty."
When handing down the preventive detention sentence, he said Morris must serve a minimum period of five years.
A hearing date for the appeal is yet to be set.