30 seconds is too long for a shot. You lose the audience after 15 seconds, especially if it's just a talking head. Imagine you're standing in front of me as I tell you all this - you're not looking right at my face, looking me right in the eye for the 15 seconds or so it took to get to this point. You're looking away. You look over my shoulder at the thing behind me, you look at the editing equipment on the table, maybe look at what's on my screen. We're up around 25 seconds now, and your gaze has shifted at least half a dozen times.
In video editing you mimic this by cutting away to other angles, or to illustrative shots. Right around the end of the first sentence I cut to a longer "two-shot" showing us talking. At "to get to this point" I cut to a head-and-shoulders shot of you nodding in agreement (a "noddy shot", done after my piece to camera, getting you to look at the right height to match my eyeline). On "you're looking away" I cut back to me, and then a shot of my PC on the bench with some editing software open (bonus points for having it showing an earlier shot from this). On "and your gaze", it's back to me.
What you were actually looking at was cutting back and forth wildly, showing you something different every five to ten seconds, but somehow you didn't even see it move.