I've ridden right through the night on randonnees and 24-hour races ... and that can be quite good.

Sometimes I ride after dark in the evenings, although I tend not to like that quite as well, especially if it is chilly and/or rainy. I find it hard to motivate myself to go out for an evening ride if I know the majority of it will be in the dark.

As for tours, most of the times I don't ride in the dark unless a day's ride has taken longer than expected. However, during the month I toured Queensland, it was very hot (mid-40s), and so my touring partner and I often got up really early and cycled for a few hours, then stopped in a shady part of town or at a beach for the middle of the day, and then cycled a few more hours as the sun went down. It was just cooler that way.