Odds of Hanging On
Not letting anything get stolen on your watch (or at least handling it properly if anything ever does) will go a long way toward letting you keep your job if you want to. Or not letting anyone you're guarding get kidnapped (or at least handling it, etc.). Or not letting anything get vandalized (or at least, etc.). You get the idea.
As long as your company can maintain whatever security contract you're operating under, you should be good. Security companies are subject to economic ups and downs, just like most others. They'll hire more and keep more in a bull market (stocks are up), and probably hire fewer and keep fewer in a bear market (stocks are down).