Champion RD92

Hmm. Well I like to believe that they mature faster due to their low numbers and need to do so to survive. They are so long-lived because they develop the mature mindset early-on that is needed to live that long.

Obviously not the case in MLP as there appear to be thousands of them, but in other places.

There was that one episode with those other dragons and they seemed like teenagers, and were obviously older than Spike.

I assume the greed-growth in Secret of my Excess is something common to dragons, but not an actual stage in their lifespan. After all, the other dragon episode featured adolescent dragons who weren't giant monsters.