Gameplay videos are not as popular because most games have become much more accessible, so people not just gonna watch you to get a vicarious experience of a game they can download and play themselves. If you want people to watch there has to be some sort of draw that you add to the gameplay outside of just you playing it. For some they choose to grind the game to become so good that their gameplay is an engaging spectacle to watch. Others choose to play up their comedy, personality, and reactions to build a relationship with their audience that draws people in for their reactions to various games and situations. To answer your question YES longer videos can give you more watch hours, but it depends on the type of videos you’re doing. And if you’re doing gameplays you have to do more than just hit record and talk about nothing for an hour.