If someone gets sentenced to 45 years in prison then they have to serve at least half of that term before they are considered for parole.
In most states an inmate would have to serve at least 25 years of the 45 year prison sentence before they are seen by a parole board.
Then again some inmates may have to serve 30 to 35 years of the 45 year prison sentence before being able to see a parole board.
But in some cases an inmate may have to serve the entire 45 years in prison before they are released.
Not everyone will get paroled and if the inmate does anything bad in prison then they may not get paroled at all and have to serve the whole sentence.
45 years is a long time in prison.