Estimate a useful running time
Let the amount of explanation set the length.
Prepare
Outline the beginning, main argument, and conclusion before choosing a target duration. A target is a planning constraint, not proof of the final runtime. A fixed recording provides a stronger duration reference than an unfinished topic brief.
Work through the decision
Read a representative passage aloud with natural pauses. Use that sample to estimate the narration length. Leave room for a diagram to become readable and for a comparison to land; removing every pause can make a short video difficult to follow.
Review the result
Compare the quote duration with the prepared script or recording. If the project scope changes, request a fresh quote and check the new authorization before starting another run.