Depends on the situation. 5 years is actually not that long. A captain will often retain his rank doing only that amount of time while someone else is acting captain. But 10, 15, 20 years, especially if they are fairly old, there is more of a chance they will step down and someone else will take over. But there are some guys who carry enough clout that it doesn't matter how long they've been behind bars. Tino Fiumara was a good example. He was in and out of prison for years and years and he was always recognized as the official captain of his crew, while Michael "Cigars" Coppola was acting captain/co-captain.