I follow a bunch of World of Tanks players on YouTube and on Twitch and going by comments made by one guy it's actually quite involved and time consuming stuff.
The guy Maxx is talking about, if his content is always like that, will most likely lose his audience but someone like WOT player Quickybaby who are actually really good at their chosen games spend 6 to 8 hours 2 or 3 times a week livestreaming, plus they have to power through bad runs of matches rather than just give up because they are running the livestream. If they also post on YouTube each 20 minute video can be the equivalent to a full working day by the time they get gameplay worth posting, edit it and add a commentary to it, and several of them put out new content on a daily basis too.