one on one: about 5min, more: around 8 to 10min.
This is an average. Furthermore I noticed: "how bigger the audience, the faster they go in." this because of the anxiety that makes the "escape-mechanism" go into effect earlier.
I had exactly the same situation. . I settled on a 4 minute pre talk and had them up and into my first routine by 10mins.
35 minutes still seemed like a very short time so keep the scripting tight.
I was encouraged by a decent stage hypnotist to have a small row of chairs (I started with 4 and ended up with 6) and to point out that spaces on stage were limited and time short so I was looking for the best, those most up for it, with the best imaginations etc.
In other words turn it into a bit of a competitive atmosphere rather than my usual all inclusive intro. It worked well, although it was a University crowd and they bought into this easily.
Hi James, My pretalk varies from audiance to audiance. I entertain at a bar or club once a week and my pretalk is as follows.: Hi ladies & gentlemen, I' m hypnotist Don Rice and I'm happy to be here at Joes bar. Here are the answers to the question you haven't asked. # I No I will not force anyone to be on stage with me, but in a few minutes I will accept volunteers. So when I say welcome volunteers you can join me on stage and take a seat. Now here is an absolute fact if you don't join me on stage the show will SUCK. #2 Is yes you will awaken from hypnosis. We have this club booked until 10.00 pm so you will be awake and out of here by then. Right now at this very minute is your one chance to become a star by joining me on stage. OK, fill the seats and the show will start. Then I do a one hour show.
I do large groups (250) or more three times a month and I have a different pretalk that lasts about ten minutes followed by a one hour show.
With any size group from the moment they sit in the chair until I start the first skit is 4-5 minutes.
I streamlined the whole show down to 35 minutes, with about 8 minutes for pre-talk and induction. It went well.
Fortunately, the conditions which required that I work that fast were eased by the end of the weekend, so I was able to do about 50 minute show by the end. (I did a total of six shows that weekend.) While I'm glad I had the exercise of having to streamline it all, it felt good to have more time.
Having thought more about this James I consider my 'pre' talk, I hate that term because it makes it sound like this is something you do 'before' you begin entertaining and enthralling your audience, and the 'tests' to be my first routines.
And as my VO intro is 30 seconds then the answer is 30 seconds.