The simple, yet complex answer is to make sure you are using all the tools at your disposal to take useful action such as thumbnails, descriptions, SEO, engaging and interesting videos, etc.
While I have not reached either yet, it really only takes one video to "pop off" and perform well to get those 4k hours, but as for the videos that don't, as I said, use the tools you have (like TubeBuddy) to grow your audience with good SEO and all the other features they have.