High Holiday services are long. Very, very long. Mornings begin with Shaharit, which starts at 9 and is followed about two hours later by the reading of the Torah. On Yom Kippur there's also Yizkor, memorial prayers, and Avodah, a special service commemorating the ancient high priests, which my synagogue omits. In between are divrei Torah, commentary, by the rabbis and members of the congregation, and an occasional piece by the choir. Then there's Musaf, a repetition of the the morning with extras like the shofar thrown in, just in case you missed it the first time. On Rosh Hashonah we get to go home at 1 or 2 and eat for many hours before returning for a brief, pre-dinner evening service. On Yom Kippur everyone comes back for Minha, the afternoon service, and stays through sunset for Ne'ila, the "closing of the gates," which concludes with all the children in the congregation processing through the darkened sanctuary with (battery-operated) candles, and a final, triumphant blowing of the shofar to symbolize that God is done writing in the Book of Life until next year.
(Well, not really. The Book traditionally doesn't "close" until the holiday of Hoshanah Rabah a week later, so we get another couple of days to finish atoning.)
It's an exhausting--in a good way--marathon of prayer.