DMs also get exponentially increasing space to build crazy challenges, because even infinite dragons is something the pc's might be able to deal with.Not that I disagree, but what about high level play is fun for the GM? I see a lot of advice here that boils down to, "Your PCs are super powerful now and can do what they want, more or less. Deal with it." The problem with high level play is it widens the gap. Players get more cool stuff they can do, including ways to ignore challenges that used to actually be challenges. GMs just get expotientally increasing headaches.
If you like going big, running epic games lets you go as big as you can imagine.