It depends on how you intend to use it. But people do have short attention spans. Therefore, it is important to keep the video short and to the point while still obtaining all the necessary information.
The video only needs to provide enough information to get viewers interested in taking the next step (buy product, give you their contact info, try for free, and so forth).
We typically recommend:
60s – Explains calmly most products or services.
90s – Explains in-depth your service or product. Includes a winning sales pitch.