Personally @Blogging Betty Boomer I would strongly advise you to add your face. Prospective students like to be able to put a face to the name. They like to feel they have a relationship with you.
In you feel shy they spend 5 minutes every day filming yourself then watch yourself. In no time at all you will start to feel comfortable in front of the camera.
You don't have to, and in many of those 30-40 hours courses, especially programming or software-related topics, it is very difficult to record them with high-end cameras for that long. I think the topic may also play a role.
However, I do use my face along with the content for the following reasons:
1. It increases trust. Students bond better.
2. You can make a great first impression with a smile and confident body language.
3. Often, the entire material is not made of ppts, whiteboards, or demos. Sometimes, you may want to take 4-5 mins to explain things. Without your talking head and hand gestures, you will have to put a ppt slide as a still image and a voice behind it for saying the stuff you want to say. You would expect students to stare at the same ppt slide for 5 mins, but the students obviously won't. They are distracted in 30 secs.
4. During the pandemic, everyone got used to the camera-driven meetings and lectures. Pre-covid, I had done so many successful webinars, where the speaker won't appear and would still seem fine. Not any more.
5. It is also a good branding technique if you want yourself to be recognized as an expert beyond your course chapters.
You don't have to. As explained above, there are advantages to doing so, but it partially depends on your choice of subject.
For me, I do screencasts, and I think that screen picture is more valuable than a picture of me on it. So I just do an introductory video and a concluding video to camera, and leave the rest as screencasts.
However, if you are in a non-IT field, then there may be more value to people seeing you.