Odds of Hanging On
As long as you're keeping a clean shop and aren't ruffling any feathers, you're likely to hang on for quite some time in this field. Janitors tend to fly under the radar, which can be both good and bad. The biggest issue you'll face will likely not be with your employer, but with yourself.
Your body will ache, your mind will be restless, and your self-esteem will take a serious hit when you're emptying the garbage and someone throws a banana peel at you. For some, a steady paycheck is enough of a reason to keep going. For others, those neon exit signs take on a much greater meaning.