You'll need to find your own metaphor in this one, given that my family and I are on vacation this week. We spent yesterday at the water park. They have one of those continuous Wave machines where you can "surf" on one of those boogie boards. A turn lasts as long as one fall (two if you fall early in the ride). In order to keep the ride moving, there's a lifeguard at the bottom who guides the rider through various skill tests. The rides last about the same amount of time for each rider even though riders are of various skill levels, and the reason is that nobody ever gets to rest on their laurels on this ride. Even the experts are pushed to the point that they take a fall every now and then, which means that everyone gets a chance to ride. Everyone has fun, and everyone is constantly pushing to improve.