Since they met at night in Acts 20:7ff, does that mean Christians today should only meet at night?

Answer:

See also: Following Bible Examples; in particular the section on distinguishing between the incidental and the essential.

"Now on the first day of the week, when the disciples came together to break bread, Paul, ready to depart the next day, spoke to them and continued his message until midnight. There were many lamps in the upper room where they were gathered together" (Acts 20:7-8).

In this passage we note a number of things about the assembly:

1. It was done on the first day of the week.
2. The preacher spoke until midnight.
3. It was at night.
4. They used lamps for lights.
5. They had assembled in an upper room.

Now are these incidentals or essentials?

1. The gathering on the first day of the week, we are told was because that was when the disciples came together to partake of the Lord's Supper. Thus, we learn that it was their practice. Combined with the fact that no other time is mentioned for the gathering leaves us to conclude that it was an essential element.
2. The preaching went to midnight because Paul had to leave the next day. This doesn't lead us to conclude that the church typically had sermons going until midnight. Nor do we find other examples where sermons always went to midnight. Thus we conclude it was incidental to this one particular meeting.
3. The lamps go along with the fact that Paul preached to late in the evening. But nothing in the passage actually tells us when the meeting started. If the disciples were using Jewish time, then the first day of the week would have started at sundown (about 6 pm) and we see that the gathering did not break up until after midnight. If the disciples were using Roman time, then the first day of the week starts at midnight and there isn't any way to narrow how long the gathering lasted. While they were together at night, notice that the time factor for the gathering was the first day of the week. It was not a certain day of the year or a certain day of the month. Nor are we told that the disciples had a habit of gathering at a certain time of the day. They gathered because it was the first day of the week. The fact that this gathering happened to be at night then is incidental.
4. The use of lamps for light is to be expected from that period of time. Does this mean that only oil lamps should be used to light assemblies? There is nothing in the Scriptures indicating that the lamps served any purpose beyond giving light. We can use this example to say it is proper to provide artificial lighting when it gets too dark to see, but the specific type of light is incidental to the event.
5. As mentioned in the sermon outline, we look at many examples of the disciples gathering in a variety of places and conclude that where disciples gather is incidental. What is essential is that they do gather.

If a congregation decided that evening works best for its members, then they ought to pick the time of day that works best for those who attend. As an example, I have a historical quote about Christians gathering before dawn for worship in one of my reference books. The reason was simple, it was a slave society at that time and that would be the best time for Christians, who were slaves, to meet -- before their masters awoke for the day.

In this example, we see that Paul must leave the next day. He packed as much as he could into the short time that he had. Thus we aren't surprised that the church was gathered long into the night. But we don't conclude that all services were like this. Paul's travels were the cause of the late service.