Odds of Hanging On
If being available to students at just about any time for just about any reason puts pep in your collegiate step, then you could hang onto this job for quite some time. It's not a career that you need to be young for, and you probably won't be fired unless you do anything outrageous.
Do a good job, keep the good of the students in mind, and you'll hold onto this job as long as you want it.