At a previous job I knew this person very well, she was actually my manager for over a year. Unfortunately when I left I didn't really keep in contact with her and I haven't talked to her for around eight months. I feel like she would still remember me as I was one of her star employees, but I feel awkward listing people whom I never talk too anymore.
Another person was the group leader of a volunteer group with the local police department, whom I often listed as a reference whenever I've applied for security-related jobs. She knew me for three years through the program, but I've been out of the program for three more, and out of contact.
Is it still acceptable to continue listing these people as references on my resume and job applications? At what point does a reference "expire," if ever?
Note: Verbal authorization was obtained to list these people as references previously.