In the Haggadah we read: "R' Elazar ben Azaria said 'Although I am only eighteen, I appear to be seventy years old, and until Ben Zoma expounded that כל ימי חייך includes nights, no one would listen to me to say the third parsha of Shema, which mentions יציאת מצרים, at night.'" Many Meforshim are puzzled by the beginning of R' Ealazar ben Azaria's statement. Why does he mention that he is like 70 years old? What impact does that have on the rest of his statement? R' Shaul Yedidya Taub zt"l, the Modzitzer Rebbe gives an interesting answer by first raising another subject. What was the סברא of the מחלוקת between the Rabbis and Ben Zoma? It went as follows: Bnei Yisroel was really in Mitzrayim only 210 years. However, Hashem told Avraham that they would be there for 400 years! There are two basic answers to answer the obvious contradiction. One תרוץ is that the work they performed was so intense, (עבודת פרך), they accomplished 400 years of work in only 210 years. Another תרוץ is that they were forced to work at night and subsequently were able to roughly cut the time in half. R' Elazar ben Azaria maintained the reason was because they worked at night. Therefore we should say the third parsha of Shema at night, since the miracle of Yetziyas Mitrayim included nights. The Rabbis held they did not work at night and it was only the עבודת פרך that enabled them to leave after only 210 years. Therefore they felt there was no reason to say the third parsha of Kriyas Shema at night.
תוספות in Shabbos 10b gives an explanation why Bnei Yisroel had to do עבודת פרך in Mitzrayim. Hashem is תובע ביקרי ד'צדקיא. Hashem is jealous of and defends the honor of a tzadik. Because the עשרה שפטים did not treat Yosef honorably Bnei Yisroel was punished by having to do עבודת פרך. Since they had to do עבודת פרך as punishment for Yosef's not being treated properly, they could not use that back-breaking labor to reduce the 400 years of exile. It is apparent according to this תוספות that the only way Bnei Yisroel could have gone out after 210 years was by working during the night.
Why did R' Elazar ben Azaria look like he was seventy years old? The gemara (ברכות כ"ח.) says it would have been embarrassing to R' Shimon ben Gamliel to have an 18 year old youngster be Av Beis Din while he himself was demoted from the position. So Hashem who is תובע ביקרי ד'צדקיא performed a miracle and caused R' Elazar ben Azaria looked like he was 70 years old. This is the reason R' Elazar ben Azaria said that he looked older than he was. This is proof that Hashem is makpid on a Talmud Chochom's Kovod, and if so, Bnei Yisroel was punished with עבודת פרך for the violation of Yosef's kovod. They must therefore have worked nights in order to go out after only 210 years, and one should thus be required to recite the third Parsha of Shema at night. That is why R' Elazar ben Azaria started by mentioning that he appeared to be much older although he was really only 18.
This is a work in progress. Much thanks to my brother-in-law Yankey Mirocznik for sharing this with me, and my brother Eli for his suggestions.