A lot of people underestimate the potential lifespan of a pet reptile. Leopard geckos can also live for up to 20 years--and so can corn snakes.
Always keep lifespan in mind when selecting a pet. Although I may get razzed for suggesting it, if you intend to keep your pet for a long time, but think you may need to eventually sell it, select a female. It's difficult to find a home for an adult male ball python, but it's fairly easy to re-home a female. I would never suggest such a thing for snakes that get larger, but there is no lack of people willing to purchase or adopt an adult female ball python.