It is necessary to add humor to big and long going presentations so as to keep the audience listening. Try to use interactive humor drawn from the audience itself observing and reacting accordingly, needs strong manipulations, but remember, you are not there for entertainment, don’t get carried away by the positive response, and even if they don’t respond as intended, just get back to exactly what you are there for- the context of the meeting.
In a presentation of say about an hour, you need to refresh by sharing something new or by creating a WOW for some fact, things needs to be done after say about every 10 minutes or after every 20 lines of speech. Remember to keep up the hear-ability of the audience. Add humor to your presentation / speech but DO NOT MAKE IT A JOKE!!! Your message should be rightly delivered as well as received and conceived.