Parents with little kids like to go early. I went on the 4:30 tour once, and, you are right, it wasn't quite dark when the tour started, and some of the houses hadn't yet turned on their lights. But the trolley driver stopped in front of the unlit houses and clanged his trolley bell. Then everyone on the trolley shouted in unison, "Turn on your lights!" The kiddos liked it, and sometimes it even seemed to work.