Technical repair and historical knowledge, including protecting valuable artwork or re vectoring from the original designs. A person moves onto higher levels of expertise, along with meeting collectors of the community that do the areas of work.
Simply implied, the people are equal, if not more important for sustained interest, not the machines necessarily themselves. The games don't change, if they were made 1-100+ years ago, they are the same games. There are many substantially creative people in this hobby, some with even more incredible motivation.
Someone one said it best a long time ago, "If you remain a pinball collector long enough you will end up touching every aspect of pinball machine repair including carpentry, design, programming, troubleshooting, soldering/desoldering, basic and advanced electronics, electromechanics, artistry, and reproduction and by doing so the people that are the experts in their fields."
This also includes teaching, as everyone starts at the beginning at sometime in their life.
Being a neophyte is not a "bad" thing.
A person will get bored with just being a player and owner eventually, as the "center does not hold".
The amount of time before this happens varies by the individual, how much they play, and the amount of cash in their pocket.
That is why you see the common "winking out" of owners like a star when they reach their personal limits, or at least downsizing at a minimum. For the latest generation of owners, the wheel of time is turning again.
A person will know when they see it, a person will say something like, "I own X pinball machines (or X $$$ of games), and I never play them. Should I sell them and use the money for something else?"
Watch the posts even on this website, it's a personal choice, not a groupthink answer, but gets asked all the same.
This means a person is close to pinball burnout and leaving, whether temporarily or permanently.
Personal age plays a factor as well.
Pinball machines are very time consuming devices to keep running, much more than many other hobbies/operation.
If you play them, they will break down, although not really a concern for most when they get into the hobby initially.
"Every pinball collector passes through the same six phases in their lifetime. "Curious George", Player, Owner, Collector, Restorer, and finally Hoarder. The place that you stop depends on when you start in the age of your life, and how many times you regress to a previous stage based on time, other life commitments, and of course, money."
Added over 4 years ago: Another example of "winking out":