Many recommend at least 400 words. I recommend at least 800, for Google ranking purposes. Part of Google's ranking mechanism is how long a person stays on your site. If you make a page too short they will read it quick and move on, which can degrade your rankings. As such, providing more text - and some good on-target videos - you can keep the reader on your page longer and might even get a click out of them.
I hope this helps. :)