How long did the air liquide interview last?

Last Friday, I just received an offer from Liquid Air China Headquarters. After receiving the telephone interview, I went to the interview three times. I asked personnel mm why it took so long. She said that al's normal interview usually takes one month, and some take two months. I calculate quickly, but generally speaking, if they are interested in you, they will tell you on the spot and immediately inform you to arrange a follow-up interview.