Starting Shavuos On Time

There is a big debate over the reason why the custom developed not to start Shavuos early in the evening, like many do for Shabbos in the summer, but rather to wait until complete nightfall. I've never been convinced by the reasons offered but I think I have figured out the simple reason why most synagogues are strict about this: It is easier to stay up all night learning if you don't finish dinner until 11pm.

If you start Shavuos early, say 6:30 or 7:00, then you will probably end dinner around 9:00. Then you will have to sit and learn for about 6 to 7 hours straight (or arrange for 6 to 7 hours of lectures). If you start at 8:00 then you won't finish dinner until 10:30 or 11:00. Then you won't start learning until 11:30 or 12:00. That's 4 to 5 hours of learning straight, which is not easy for the average layman but much easier that 6 to 7 hours.