Odds of Hanging On
Once you're the mob boss it's pretty difficult to be knocked off that pedestal. However—and this is a massive however—there will be rival Dons, a certain number of wiseguys, and every member of law enforcement who'd like to see you gone—wiped out, invisible, six feet under or with concrete shoes on at the bottom of the lake.
Or behind bars. They'd probably be cool with that too.
Once you're in the Mafia, getting out of it is just about impossible unless you enter the Witness Protection Program—and even then, you'll be watching your back for the rest of your natural life.