Don’t provide more than 15 years of experience. We’ve all had crummy jobs in high school and college, and the experience you gained in those jobs is probably not relevant to the job you’re applying for now. So don’t list those jobs. If you do, it not only shows you in a somewhat unprofessional light, it also enables employers to estimate your age — and nobody needs to know that.
We once had a Controller candidate include her high school job with Hot Dog On a Stick on her resume. She probably makes a mean lemonade, but this early experience won’t help leverage her into a responsible professional position.
On the other hand, you don’t want to list only your last two years or jobs because they’re in the same field as the position you’re applying for. Interviewers like to see the progression of the jobs that make up your career path — preferably a path that shows growth and progress.