The night before embarking on the Tongariro Alpine Crossing we had honest to goodness plans to go to bed early and get lots of rest before our all-day tramp. Then we started a puzzle with a couple of South Africans, and...we were up until 10:30 doing that puzzle. We're reckless.
We got up before dawn so we could drop our car off at the end of the trail and then take a shuttle to the beginning. I definitely recommend getting an early start. Apparently some people have done it in as little as 7 hours, but I'd be surprised if those people ever stopped to look around. It's hard work, so you might as well take your time and enjoy it. Given that we're not very fit, have a penchant for lots of mini picnics, and a tendency to wander, we took closer to 12 hours to complete the whole thing. Another good reason to get out early? Dawn over Mt. Ruapehu. For us it was all aquamarine with neon pink clouds that wisped over the mountains like a rooster's tail. Just unforgettable. It's the best thing I have ever wiped fog off a car window to see. (So far.)
What I don't recommend is going on Waitangi weekend. There were so many people on the track, and there were times, especially at the beginning, when we felt like cattle. I'd love to go again another time when there are fewer people out. Also, be prepared for really harsh sun. I needed sunglasses even before the sun crested over the mountains. Once it rose over the ridge I could barely see my feet in front of me. Until the sun got a little higher in the sky I could only take in the view if I hit a patch of shade or stopped and turned around, which always startled the herd.
That said, it was still an awesome experience.
After the lakes the crowds thinned out. Although it's posted as a one-way hike, I saw a lot of people turn back the way they came. As long as the weather isn't too wet, I could see that going fine, although you do miss out on some beautiful stuff by going back early. The rest of the hike isn't as famous as the first half, but it was honestly the part I enjoyed most. Maybe it was relief at not being around so many people, or it could have just been refreshing to see land looking kind of green again after so much volcanic rock. There are some stunning steam vents, gold and grey colored streams, and it's such a nice, gentle slope down that it feels really relaxing by comparison. Eventually the plants grow thicker, the trees get taller, and you're back in the familiar world.
Then you realize how exhausted you are.