Odds of Hanging On
To make it in this field, you have to be tenacious, adaptable, and extremely meticulous. Meticulous like a rocket surgeon. There are those who fizzle out after their first few gigs, but they probably weren't cut out for this sort of work anyway. The more work you do as an audio engineer, the more experience you have, and the bigger your network grows.
Essentially, the longer you're in the field, the better chance you have of staying. As long as you keep your skills sharp and don't step on the talent's shoes when you meet them, you should find it pretty easy to find work.