It sounds like the Invega sustains is working - and keeping the voices away. Thats a good thing, most of us here think.
The stress of psychosis causes brain damage - and the medications help prevent that, and also many other things - like loss of housing due to bad decision making or conflicts, etc.
Many people here are on Invega here - and while its far from a perfect medication (is there such a thing?) the benefits outweigh the negatives.
I recommend you read this recent research:
Gray Matter Loss in Brain Due to Psychotic Episodes / Schizophrenia, Not From Medications