I think MLP was so organized because there was just sooooooo much stuff to keep track of. It's still active because you can never really be done collecting ponies (as long as you want to keep going). Even if you finish your Americans, there are always Euros, nirvanas, and accessories to hunt down. I guess SSC has had several production runs too, but I think ponies still have them beaten pretty easily for near-continuous production over the last 30 years. Since there's so much more, pony collectors just never get bored.