Shortly after freeing Neo from the Matrix, Morpheus tells him:
We never free a mind once it's reached a certain age. It's dangerous, the mind has trouble letting go. I've seen it before and I'm sorry.
Later on, in conversation with Agent Smith, Cypher remarks:
You know, I know this steak doesn't exist. I know that when I put it in my mouth, the Matrix is telling my brain that it is juicy and delicious. After nine years, you know what I realize? [Takes a bite of steak] Ignorance is bliss.
Cypher has clearly been an adult for much longer than nine years. The actor playing him, Joe Pantoliano, was 47 years old at the time of filming, whereas Keanu Reeves was 35. So it would seem Neo and Cypher were both in their 30s when they were freed from the Matrix.
It is possible that when Morpheus says "I've seen it before", he is in fact referring to Cypher. It might help explain why Cypher is so bitter about leaving the Matrix and wants to go back.
So the question is: Why was Cypher freed at such a late age?
The above question may not have a canonical answer. So, as a secondary question: Is there any in-universe information about what happened when Cypher was freed from the Matrix, other than what is mentioned in the film?