Odds of Hanging On
Well, there's good news and bad news when it comes to hanging on.
The good news: despite dramatic depictions in television and film, only fifty FBI agents out of the tens of thousands who have taken to the field have been killed in the line of duty (source). While obviously tragic, that's a fairly small number for a law enforcement agency that's been operating since 1908.
The bad news: the FBI is notorious for its changes and restructuring, so you're not exactly guaranteed to be an agent for life. Of course, if you do your job and don't try to sell state secrets to the Russians, you'll probably be okay, but you never know. Just make sure you do your duty, and you'll just have to weather the eventual cuts in government funding as they come.