For better ranking or increase the watch time of the videos it has become trend to make longer videos. That is the only reasons for making longer videos for last few years.
Since watch time is the most important along with not getting bored is key ranking factor on YouTube, every creator wants the biggest piece of the pie for themselves, hence they make longer videos.
Variables that can distort the results may be:
1) The type of channel/video (Dj channel, Cooking channel, vlog, tutorial, review etc.)
2) The age of the audience
3) The language
4) The geographic target
5) The video host
On motivational channel the target audience is more patient than review channel.
30 minutes of videos can easily reach 50% audience retention for motivation channel on the other hand review channel lots of effort and hard work on 15 minute video to get a 50% audience retention even host for both channels is the same, the topic is different.
Without getting it bored you can make videos as long as you can and also make sure never
1) Make videos for the sake of making it longer.
2) Some topics just don’t have enough meet the completion for a 10 minute video but make it informative and complete which make some sense to your viewer. Exaggeration of the topic can reduce the interest of your viewers that can affect your subscriber. YouTube suggestion can effect largely on your channel subscription which promote those videos which generally liked by most of the viewer.
3) Our suggestion is to examine your target viewer than make videos.
Best YouTube video length for monetization
Always remember, there is no minimum length for monetizing your videos.
But for the sake of optimal revenue, make your video at least 10-12 minutes, because you can place extra mid-role ads in the video.
You can place as many mid-roll ads in your video as you want, however that is not the optimal viewer experience.
Three mid-roll ads in a 30 minute video are too much in our opinion.
1) You can place pre-roll, mid-roll and post-roll ads.
2) The post-roll ads are switched off by default.
3) Use all three to optimize your video revenue.
What is the maximum length of the videos that can I upload on my channel?
15 minutes of by default videos you can upload but after verification of your channel you can easily uploads 128 GB (12 hours) of videos.