Videos are hosted in IPFS. They will stay as long as the video file is pinned by someone and kept alive on IPFS. DTube developers promised that they will keep the videos alive for 7 days which is the payout period on Steem.
After that, if the video had a payout of over 10 cents, it will be kept. According to the following reddit thread:
> Old videos (7 - 14 days old , or older, depends) are cleared from the IPFS cache automatically if they don't get any upvotes anymore or have at least $0.10 after 7 - 14 days. That's because after all we aren't Google and video hosting is like the most expensive thing you can do on the internet. You can prevent it from happen if you set up your own IPFS node on a cheap VPS and keep the videos online this way. This also supports our platform. So if your video gets constantly upvoted or has at least 10 cent before the cache clears, it stays online. it can be online for a theoretically unlimited time.
>Hope I could help you.
> Link: https://www.reddit.com/r/dtube/comments/87g48n/old_videos_wont_play/
If someone wants to keep his videos alive, he may pin them himself by renting a VPS server. The reason only popular videos are kept is because of the high cost of hosting videos.
The videos will be there for seven days, after seven days if it will be deleted. If you want to keep that video on streaming you have to pay, or the audience by up voting the content.
Only links are stored in block chain, videos are stored in different servers which are not in block chain. The storage has it's cost. So, those videos earn will be last long or paid videos.
For seven days, it will be there for sure.
I think I am right.