I have so many clients that ask me how long they should wait in the lobby for the interviewer after they have signed in with the lobby receptionist. I tell them, please don’t wait any longer than 30 minutes. Your time is very valuable and you need to respect yourself or they wont. After 10 minutes you should walk up to the receptionist and ask how long will it be until the interview, then relax and sit back down. If you are still sitting in the lobby 30 minutes after the time you are supposed to be interviewing, then you need to sign out and leave.
There are only a few reasons that you should excuse the interviewer for being late. 1) If the interviewer was called into a last minute meeting 2) If the interviewer was sick at the last minute 3) If the interviewer was really backed up in traffic because of an accident.
Just remember, the way they treat you during the interview process is the way they are going to treat you on the job and vice a versa. If you treat them with little respect or are unresponsive, they will assume that is how you always are and they will be apprehensive to select you as a top candidate.
Years ago I read the “Knock Em Dead” books by Martin Yate and I especially loved the “Knock Em Dead” interview books. So check out the link and starting preparing for the interview, etc. by reading these books. https://www.knockemdead.com/