Odds of Hanging On
Well, there's good news and bad news.
The good news: Despite dramatic depictions in television and film, only about 50 FBI agents have been killed in the line of duty since the Bureau's inception in 1908. The NYPD has lost more than that from car crashes, and they only started using police vehicles in the 1920s. Think about it: That's an average of around half an agent a year for over a hundred years; but since it's hard to kill half an agent, it's probably better to say one every two years. (Although there are plenty of Americans who would complain that their job has killed their soul or taken half of their life away, that's not exactly what we're talking about here.)
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 keep your head down. And don't get greedy. Or treasonous.