This kinda thing is common when your a kid. You always have big plans, and get really gung ho to go do them. Then something comes along and you get distracted (OOh a butterfly!) What was I talking about? oh yea.
An example would be the HL2: EP3 project that briefly appeared. It had some good momentum to start out with, but I think people started realizing just how much work needed to be done, and so it petered out. When I first seen the project, I had a prediction that this would happen, it's an extremely common occurrence among new mods and projects.
That said, just because you might find a project wasn't practical to finish in the end, doesn't mean something cant be learned out of it. So that's why I like to see project like that show up, because its all just part of the process to learning how to make stuff.
I'd say over half the projects I started when I was your guy's age I didn't complete, and they would start to accumulate in the garage, much to my moms ire. But after a little while, I got tired of not completing projects to what I wanted them to be so I started finishing them.
Krasher is in this stage, as well as a few other people on the forums. Which isn't a bad thing, it just means projects get announced and then just disappear into the ether. But eventually the will get tired of us harassing them about it, and then things will start to get done.
It's one of the hardest things to learn, and I still struggle majorly with it, but I'm getting better at it (I think)
On that note, I want mah muscle car! Go get to work!