If your videos already have been distributed as they are being watched they would still be online after you take your node offline (though there are no guarantees since others can go offline as well). If you upload your video via d.tube it would get distributed by them initially but if nobody is watching it the video will be taken offline soon after (I think after like 2 weeks), if it is being regularly watched though part of the videos income will be used to keep the videos online (though the cuts are always the same, 50% for the author, 25% for the upvoters, 25% for the platform afaik).