Upon uploading a new Video, you have the choice to decide on whether to send notification of the upload to your subscribers or not. Usually, the viewers get about 3 upload and live stream notifications within a day. For more than that, you have the choice of disabling notifications.
To do this, click on “MORE OPTIONS” while uploading the video. From here go to the “License and distribution”. Here you will find the section for “Publish to subscriptions feed and notify subscribers”. Opt against sending notifications.