a passage from "All About Eve"

[stanislaw.masny]

Birdie: What a story. Everything but the bloodhounds snapping at her rear end.
Margo: There are some human experiences that do not take place in a vaudeville house! And that even a fifth-rate vaudevillian should understand and respect. I want to apologise for Birdie.
Birdie: You don't have to apologise for me. I'm sorry if I hurt your feelings. It's just my way of talking.
Eve: You didn't hurt my feelings, Miss Coonan.
Birdie: Call me Birdie. And as for being fifth-rate, I closed the first half for eleven years, and you know it.

I don't understand the last line of the passage. What does "I closed the first half for eleven years." mean?
Best regards.
PS: I've just found another one that I don't understand. See it below:

Having covered in tedious detail not only the history of the Sarah Siddons Society, but also the history of acting since Thespis first stepped out of the chorus line, our distinguished chairman has finally arrived at our reason for being here.

What does "has finally arrived at our reason for being here" mean?

[rlfwood]

What does "I closed the first half for eleven years." mean?

The speaker is described as a "vaudevillian" (See Vaudeville - Wikipedia, the free encyclopedia if you don't know what that means). A vaudeville show had an intermission halfway through, and it was important that the final ("closing") act of the first half be sufficiently interesting that the audience would return for the second half of the show. So in saying that she "closed the first half", the speaker is implying that her act was considered good enough for that important spot on the program (and therefore not "fifth-rate").


What does "has finally arrived at our reason for being here" mean?

After a long introduction, the chairman is finally going to get to the point (i.e., talk about whatever the meeting was called to discuss).