Dtube uses IPFS technology, so it hosts your content during payout period, but it does purge videos later on unless you have pinned the content. If you include an article body with your video, that text content is stored on the chain, permanently. Because videos themselves are not kept in the chain, they are susceptible to hosting fluctuations. I can hook you up with a few groups who can help you pin to IPFS and keep control of your video content, if you like!