My channel is focused on knitting. (I currently have 1,750,000+ views and expect to hit 10K subs tomorrow.) I've had my channel for ten years, but it's only been this year that I've decided to upload content on a weekly basis. (I started the year with about 7300 subs.) Prior to this year, I uploaded videos sporadically, as reference material for in-person classes, or as an embedded video within a knitting help column I wrote 6-7 years ago on Ravelry (it's an online knit and crochet community of 7+ million people; at the time I wrote the column, there were about...a million? members. Something like that.). When I release a new knitting pattern, I sometimes create a video tutorial for certain unusual techniques. The outside exposure to my channel, particularly for several specific videos, is what grew my channel prior to this year, with me paying little attention to it. The main point, though, is that I was generating views and subscribers through related work outside of YouTube. Until I started weekly videos in February, it had been two years since my last upload.
One of the reasons I decided to focus more on YouTube was that the shop where I taught in person closed, and I needed to figure out how to channel my teaching energy. I'm also writing articles for several national knitting magazines, and shifting how I teach in-person to regional and national events, rather than at a small shop.
After nine months of uploading weekly videos, I'm getting an idea of what sorts of videos are likely to be popular pretty quickly, and which ones will gain views long term, and which ones are duds. I do have FB and Twitter accounts where I post announcements about new videos, but my main online community is on Ravelry. I help people with knitting questions in the main forums, and I have my own group Ravelry community of about 1600 people. My Ravelry community grows from my YT subscribers, but I gain YT subscribers from Ravelry, as well.
My observation is that educational content is not as reliant on getting most of its views in the first couple of days as other sorts of channels. My immediate views are from subscribers, but most of my views come from outside that base, over time, as recommended videos or because someone searched for how to do a particular technique.
One thing I have learned is that I can do a video on a topic many others have done, but I have expertise and a talent for teaching that material that others may not have, so those videos are particularly well-received. It opened my eyes to doing videos that are far more basic than I would have bothered with before, because I had thought, "Well, that's already been done, why bother?" I will bother now, because I might be able to do it better, and then those viewers can stick around and see my videos on more advanced topics as their skills improve. While more advanced, unusual techniques are of great interest to me, and I will continue to do those videos, I now understand the value of doing videos on basic information.
Do you have outlets other than your YouTube channel for teaching marketing? That might be useful to you as it has been for me.