The distinction that matters is between video somebody chose to watch and video that interrupted them. A promotional clip in a feed competes with everything else on the screen and has seconds rather than minutes. A demonstration somebody sought out, because they are deciding whether to hire you, has their attention as long as it remains useful.
For social feeds, the practical range is short enough that the format dictates it. The first two or three seconds determine whether anybody continues, which means arriving at the point immediately rather than introducing yourself. Anything requiring context before it becomes interesting will be scrolled past regardless of how good the rest is.
For a video on your own website, the audience is self selected and the constraint changes. Somebody on your service page is already interested, and a two or three minute explanation of how you work is entirely reasonable. What loses them is padding rather than length, and the same content compressed is always better than the same content extended.
Testimonials and case study videos should be shorter than instinct suggests, usually under a minute. The specific sentence that matters is somebody describing a concrete result, and everything around it dilutes rather than supports. Three short clips outperform one long one, because each can be used in a different place.
Watch retention rather than guessing, since every platform reports where people stop. That curve tells you the actual answer for your audience, and the common finding is a sharp drop at a specific moment rather than a gradual decline. Something at that point is losing people, and it is usually an unnecessary introduction.
Cut the opening, which is where almost every business video wastes its attention. Logo animations, welcome messages, and explanations of what the video will cover all delay the reason somebody pressed play. Starting with the substance and putting any branding at the end is a consistent improvement.
Match the length to what you can sustain producing, because consistency matters more than any individual video. Something short and useful published monthly outperforms an ambitious production that happens once, and the shorter format is what makes a habit possible.
Then check it on a phone with the sound off, since a substantial share of video is watched that way. If the point does not survive without audio, captions are not optional, and a video that requires sound to make sense is reaching a fraction of the people who encounter it.
Produce a short version alongside anything long, since the same material serves two purposes and the short one reaches people the long one never will. A three minute explanation and a thirty second extract from it cost almost the same to produce and go to different places.
Front load the value regardless of length, since the decision to keep watching is made in the first few seconds and nothing later compensates for a slow start. The strongest point belongs at the beginning rather than as a conclusion.
Check the file size as well as the duration, since a long video hosted badly slows the page it sits on. Serving video from a platform built for it rather than from your own hosting removes that cost entirely.
Write the point in one sentence before recording, since a video that cannot be summarised in a sentence is usually one that has not decided what it is about.