Odds of Hanging On
As we've said, there's no shortage of people with back pain. Also, let's be honest—people aren't going to stop getting in car accidents anytime soon (unfortunately).
And even though significant portions of the medical community have been calling quackery on chiropractic medicine for a while now, the spine docs still manage to remain in business. So as long as you don't get sued too often, and can keep a relatively broad clientele, there's no reason you can't have a nice, long career.